It should be obvious that, since they are playing the lowest stakes possible, most 2NL players are “bad” poker players, but this doesn't tell the whole story. You cannot treat every player at a certain stake level in the same way. 2NL players will typically make more mistakes than 25NL or 50NL players, but every player at every level has leaks in their game. I have leaks, you have leaks, TheLangolier has leaks... everyone has leaks. This is why even solid winners have to adapt their styles and make "villain-dependent" adjustments to keep their graphs moving in the right direction. You'll come across a wide variety of player types at 2NL, and each needs to be dealt with in a different manner. Fortunately, you can make money at 2NL if you're not a particularly strong poker player, primarily because the mistakes you make will be smaller and less frequent than the errors made by your opponents.
Since we make money from our opponents' mistakes, it's helpful to know the tendencies of each player in order to exploit his most frequent mistakes. In this article, I'll be outlining the most common player types, providing the sort of stats that will show up on your HUD (if you use one) that can be used to identify and colour-code them, and giving advice on the best ways to maximise your profit when you get involved in a hand with each type of villain.

There are two main ways in which a player is described: How loose they are, and how aggressive they are. A loose player plays a lot of hands and a tight player plays few hands. An aggressive player does a lot of betting and raising; a passive player mostly checks and calls. Using these terms leads us to 4 main player types, which I've listed with the most commonly-used shorthand terms for them.
Loose Passive (LP)
Loose Aggressive (LAG)
Tight Passive (TP, more commonly “nit”)
Tight Aggressive (TAG, often called a “reg”, short for “regular”)

The poker community has developed its own patois for the various player types. The loose-passive playing style (which is NOT a winning style of poker) is much derided, but these guys are our main source of profit, so we should welcome LPs into our games. You'll hear loose passives being referred to as fish, whales, calling stations, donators, producers, or ATMs. Without loose passives in the game, poker becomes hard to beat. A winning style for most games is tight aggressive (TAG), and that's the style I've advocated in my blog series. At the lowest stakes, playing a nitty “weak tight” style can also be profitable. At higher stakes, the LAG style becomes more common. Most of the famous poker players you've heard of are LAGs, or are at least capable of adopting a LAG style when a +EV situation arises. Perhaps trying to emulate their heroes, many 2NL beginners try playing a LAG style, and in most cases it fails abysmally, because the LAG style requires superior hand-reading and villain-profiling skills and expert post-flop decision-making with less than stellar starting hands. There are many bad LAGs at 2NL. Indeed, they tend toward the “maniac” end of the spectrum, and can be a great source of profit if you have the nerve to stand up to their aggression.

My primary tools for exploiting my opponents are my HUD stats, colour-codes, and player notes. I like to have everyone at my table colour-coded within one orbit, even if it's just to indicate that I've seen them before. This helps me with table-selection in the lobby, as it means I'll at least have a few stats on someone if they are marked in grey, even if I've not yet picked up a good read. (See my previous blog for more on table-selection).
The colour-coding chart that I use in the Pokerstars client is somewhat esoteric, as I use many more colours than most. I used to have a separate range of colours for tournament players, but this made it even more confusing, as someone that I'd identified as a loose aggressive player in a freeroll tourney might turn out to be tight passive in a real money cash game.
Here's the colour-chart I'm currently using for cash games:

Colour code chart

If you're a totally new player and haven't set up your colour-codes yet, then I would recommend you adopt the popular “traffic light” system. By this, I mean your three main colours are Red, Orange and Green. Red is a warning colour. It means STOP... and think. It's ideal for players that appear to be solid, tending towards tight-aggressive. Most nits and TAGs fall into this category. At the other end of the spectrum is Green for GO... to Valuetown. Orange can mean proceed with caution. You may like to use this colour for players that are somewhat loose and somewhat aggressive.
For player types to whom you want to pay particular attention but don't quite fit this scheme, such as maniacs, you can use a different colour. I also have two different colours just for short-stackers:

With my colour-code chart in mind, I'll now profile the common types of players, give example 2NL FR HUD stats for them, and give you some tips on how to exploit them.

Loose Passive

Loose Passive (LP)
Loose passives are the guys that play ASAP (“anything suited, any position”) and call too much. They limp into pots, call your isolation raises, and then chase every gutshot to the river, no matter what percentage of the pot you charge them. These guys take the view that “It's not the best hand pre-flop that wins. It's the best hand at showdown that counts”. If a player is going to showdown more than 30% of the time, when he typically started the hand with a weak hand, it means he's calling down with any pair. Sometimes he'll look you up on the river with ace high on a paired board containing 3 cards to a flush, apparently because he thinks you're bluffing. Loose-passives will rarely bet or raise. These guys love slowplaying their monsters. It's pretty sick when you go for 3 streets of value with AK on KQ8xx and the calling station (who naturally limp-called pre-flop) just calls every bet, before proudly flipping over a set of queens. Since they slowplay so often, these are the guys who'll allow you to suck out occasionally. They will bet so small (or even check) with hands like top set that you can make flushes and straights for a bargain price.
How to exploit Loose Passives: Since these guys are calling stations, you shouldn't bluff. If they fold to flop-bets less than 40% of the time, you shouldn't even c-bet if you have air (like AK on T63). Note also that an ace on the turn is not a “scare card” to a calling station, because LPs will routinely float the flop with various ace rags. Your plan should be to make top pair (or better) and then go for big fat value, by betting close to pot on every street. TPTK is effectively the nuts against these guys, so you should treat it as such. If you happen to get raised by a calling station (a very rare occurrence), be very afraid. You should be able to fold top two if a calling station raises the river on a board of KQxxT, because he always has a straight.

Semi Loose Passive

Semi-loose Passive (SLP)
Semi-loose passives are somewhat similar to calling stations, but seem to have a degree of pre-flop hand selection and post-flop discipline. They might have even flicked through a poker strategy book. They know that JTs is significantly more playable than J7o (so they fold the latter pre-flop), but they don't recognise how hand selection should change according to position, stack sizes and pre-flop action. You'll see these guys limping QTs UTG, or cold-calling a 3-bet in the big blind with 44. Once they see a flop, the SLPs tend to be semi-stationy, but they won't chase gutshots or call down with bottom pair, especially if the price is high, as they seem capable of comparing pots odds with their outs. Some SLPs, however, will always call a turn shove with a naked flush draw because “87s is my favourite hand, it never loses!” Like calling stations, these guys get married to underpairs. The SLP might manage to raise pre-flop with QQ, but then he'll bet less than half pot on every street when the flop comes king high. If he has an overpair to the board (even 88 on 752), then this villain is never folding. You can stack him with bigger pairs and sets.
Exploiting SLPs: Be more inclined to c-bet into these guys than the total stations, especially on dry boards, as SLPs actually possess a FOLD button. Semi-loose passives play a lot of “drawing hands”, so you can go for fat value if you have TPTK+ on wet boards. As with LPs, give a lot of credit to raises from these guys. They are never semi-bluffing. They only raise with made hands that can beat TPTK. If you're in a pot against an SLP and he actually raised pre-flop and then makes a decent-sized c-bet (indicating he has TPTK or an overpair) go for maximum value with a big raise if you have a set or better. These guys are incapable of folding TPTK and will absolutely stack off with it, even if it takes you 3 streets to get all the money in. (They always just call the flop raise and never 3-bet/jam without the nuts).

Loose Aggressive LAG

Loose Aggressive (LAG), Semi-Loose Aggressive (S-LAG)
At 2NL, LAGs and semi-LAGs are the “donks” at the table, so it's unsurprising that their favourite play is to “donkbet” into a the pre-flop raiser, whether they have a pair, a draw or total air. Call 'em what you like – LAGfish, aggro-donks, spew-monkeys – these guys think that aggression is the way to win at poker. They are half right. Aggression certainly wins pots. It doesn't necessarily win money. LAGs like to see flops, but they don't like doing so without the initiative. If they are first in, they will come in for a raise, and the sizing they use is often a tell of the strength of their hand. A minraise is usually a small pair or a suited connector, a bigger raise is nearer the top of their range. These guys will call raises with dominated hands like KT and A9 and then overvalue their hand when they flop a pair. Post-flop, bad LAGs will rarely just call if they have a pair or a draw. They like to raise. This leads to them value-cutting themselves. Since a bad LAG treats AT as the nuts on AQ5, you can win his stack by c-betting with AQ and then shoving over his raise. LAGs rarely play draws passively. Indeed, they will usually donk out or raise with any piece of the board. If you were about to make a c-bet with air, then the LAGfish's donkbet saves you money. You can just fold. When you get a hand, you can sit back, hit the CALL button, and let the LAG spew off his chips with worse.
Exploiting LAGs/S-LAGs: LAGs are the hardest players to play against, since their ranges are wide and their play is unpredictable. Mistakes you make against them will tend to be very costly, because bad LAGs tend to play bloated pots in which your whole stack is at risk once you make an incorrect call or raise. It's particularly hard to play your normal game if one of these guys is on your left. Since he will make your life hell both pre-flop and post-flop (often forcing you to reluctantly fold what is likely the best hand) it's not a bad idea to just leave the table, perhaps coming back in a better seat, so that you have position on the donk.
Use notes on bet-sizing tells to help your with hand-ranging (does he bet big with weak hands and small with monsters, or vice versa?) and have a solid plan for your hand before you reach the next street. e.g. Before you even raise a hand pre-flop, decide what you will do if you get 3-bet by the LAG. If you're seeing a flop, then visualise the action before it happens. Say to yourself something like “If I make TPTK on a wet board, then I'll pot it, and if he raises, I'll shove”. Having a plan in place reduces the stress factor, so you'll make better decisions.
The main way to exploit the LAG's aggression is to let him value-own himself. If you make a decent top pair or better, let the LAG do all the betting. Grit your teeth and just call down. A LAGtard will frequently fire all three streets with a complete airball and then he'll berate you in chat for calling his bluffs. Use his aggro-tilt against him by continuing to make hero-calls when he tries to bully you out of a pot.

Maniac

Maniac
These guys are like LAGs on steroids or a few cans of Stella. The maniac often hits the table on a Friday night when the pubs have closed. This “weekend warrior” plays like a drunkard throwing punches in a brawl. He swings... and he misses. Maniacs play so many hands (and play them so badly) that they often don't last more than a few orbits unless they get lucky and hit a random gutshot or trips to win a stack. Like LAGs, the main tactic these players use is blind aggression. They will bet and raise at almost every opportunity, and this puts a lot of pressure on opponents. It's hard to call a pot-size bet if you just have middle pair, even though it's likely the maniac has something like 7 high. Maniacs do not like folding. If you try to out-aggress them by raising a flop or turn, they are likely to shove on you, whether they have a hand or not. When a maniac loses a big pot, either because someone hero-calls his three-barrel bluff, or his top pair gets beaten, he is likely to get very angry in the chatbox, and go on raging tilt immediately, often tilt-shoving the next few hands pre-flop.
Exploiting a maniac: Ideally you want to have position on a maniac, so that you can see his actions pre-flop and post-flop. I'd recommend you tighten up somewhat, and fold most speculative hands unless you get a very good price pre-flop, because this guy is never giving you free cards post-flop if you have a draw. As with the bad LAGs, making top pair and calling down is the main way to exploit a maniac. If his biggest mistake is bluffing, then let him do it. Act weak by checking and calling with your made hands, and then come over the top on the river with a big raise if you have anything better than TPTK. If the maniac open shoves (a frequent policy when he is tilted), then my standard calling range is JJ+ and AK. A maniac that shoves 5 hands in a row certainly has many worse hands than JJ/AK in his range, but you're often no better than flipping if you call with much worse, and the variance can be brutal. With a maniac on the table, you have to remain patient and just hope you pick up a big hand before he tilts off his stack to one of the other players. There's also no law against the maniac getting dealt a real hand. Interestingly, the maniac will often slowplay monsters, so if he's been raising every hand and then limps UTG, be very cautious. He often has KK+ and is trying the limp-reraise trick.

Tight passive (nit)

Tight Passive (nit)
I use 3 different colour codes for nits, although one would probably suffice. Those with a PFR number close to their VPIP are basically playing a TAG style but a little too tightly. They tend to play the same 9-12% range (pairs, big aces, suited Broadways) in every seat, so their button raises should be treated as if they are EP opens, and not steals. It's hard to make money from these guys post-flop.
A villain playing 7/4 or 5/5 is an ubernit. He only plays the strongest hands, like TT+ and AK. These guys are easy to put on a hand, but hard to make much money from unless you flop a set when they have TPTK/overpair. Ubernits start with such a strong range that they are usually betting all three streets, so they have a high AF number. They find it very hard to fold, even when you make it “obvious” you can beat one pair. Since the ubernit so rarely plays a hand, he's usually going all the way to showdown with it when he sees a flop.
Tight players with a low PFR (stats like 11/5 and 10/3) are what I call “nitty set-miners”. These are archetypal “weak tight” players. They only raise pre-flop with legitimate monsters (QQ+/AK) but they love limping in or calling raises with small pairs and suited aces, whatever their position. In short, they are trying to make the effective nuts, be it a set or the nut flush. Weak tight nut-peddlers can actually make money at 2NL, but they get crushed at anything above 5NL, because they are too scared to bluff, and good players won't pay them off when these nits make their sets and flushes. If a set-miner makes a big bet or raise, they have a big hand. If they fire two streets on a board like QT65, your TPTK is usually no good.
Exploiting nits: The most obvious exploit is to steal their blinds. Nits fold pre-flop so often that stealing their blinds with any two cards is possible. (Try using a 2.5bb open or a minraise, as described HERE). The second exploit is to fold to their pre-flop raises unless you have a pocket pair and have the implied odds to go set-mining. It's ironic that one of the best ways to exploit a nitty set-miner is to go set-mining yourself. When you have 66 and the nit bets on J63, you should win his stack every time, unless he happens to have JJ. If a nit limps in, then you should iso-raise as normal with your high cards, and range him on Axs and small/medium pairs. You can c-bet most flops, as the nit will fold over 60% of the time. If he calls, he may be slowplaying a set, but if there is a flush draw, he's drawing to the nuts, so bet big on blank turns and do not pay him off if the flush comes in. If a nitty set-miner raises the flop, he has a set almost always. However, if the board is all rags, like 642r, then the nit will sometimes go crazy with 99-77 and I'm usually happy to stack off QQ+ in that case, as villain's range contains more second best overpairs than sets. It wouldn't be a huge mistake if you folded to every post-flop raise by a nit. These guys never semi-bluff raise with draws. It's strictly made hands for them.
Against an ubernit or nitty set-miner with a very low PFR, I'd recommend flatting their pre-flop raises when you have KK/QQ, in order to keep their worse hands in the pot. Ubernits are scared of pre-flop 3-bets and will sometimes fold a hand as strong as JJ if you re-raise. You'll get more value by trapping with KK (and sometimes even AA) and stationing them post-flop. (If you have KK, you even lose the minimum when the flop brings an ace and the nit bets into you).

Tight aggressive TAG

Tight Aggressive (TAG reg)
The TAG style is the most profitable style for 2NL FR and is the one recommended in the PSO courses and my ABC series. If you're on my table, I'll mostly be avoiding you if I've colour-coded you purple. The ABC style that most of the regs play doesn't have many holes; it's fundamentally solid as it's based on decent starting hands and value-betting. TAGs are quite easy to put on ranges if you are also a TAG. If a villain has similar stats to yours, and you see him open in MP, then you can say “Well, I'd be opening with XX in that position, so he's not going to show up with YY in this spot”. TAGs won't get “creative” post-flop very often. If they raise the flop, it's occasionally with a decent draw, but mostly it's 2pr+ and is a raise for pure value. If an ABC TAG bets two streets, he nearly always has TPTK+ or a combo draw.
Exploiting TAGs: I generally try and stay out of the way of regs, so there is rarely more than one “purple” on my table if I can help it. There's not much money to be made from playing villains that have the same skill level and hand ranges as you. If there is a big pot between two TAGs, it's usually a cooler, and the only beneficiary in the long run is the poker site that collects the rake. While TAGs are certainly bluffable, there's no need to get into “reg wars” at this level. One way to exploit TAGs is to execute the “float play”, which means calling on the flop with a plan to steal the pot on the turn. I advocate a one-and-done approach to c-betting at FR 2NL, so when a TAG checks the turn after betting the flop, he's usually giving up with two overcards that missed, so you can bet in position and take it down. I get floated a lot at 2NL. It doesn't matter that the villain isn't consciously making the float play. It's just natural for him to call the flop with any pair, and then bet the turn if I check to him. I'm usually check-folding the turn, so floating with ATC would actually work well against me. Be sure to check a player's “turn c-bet” stat once you have lots of hands on him. If it's lower than 40% (like mine), the player is a good candidate for a float. Some TAGs will barrel the turn more often, so it's best to fold your marginal hands on the flop if he's likely to keep betting.

Short-stacker

Short-stacker (SS)
I like to colour code all short-stackers (anyone with less than 50bb) as a visual warning; a reminder to not go speculating with small pairs and suited connectors. Many 2NL players (especially from Germany and former Soviet Bloc countries) will buy-in for the minimum 40bb (80c) and follow a strategy recommended by a particular poker website. Tight aggressive short-stackers often play multiple tables and follow very straightforward lines. They automatically 3-bet JJ+ and AK in every situation, c-bet 100% of flops and usually get their stack in on the turn if they have any piece of the board. There's basically no money to be made from the “solid” short-stackers, except by getting all in pre with QQ+ and beating their AK. If there are 3 or more SS-ers on my table, I'm leaving when the blinds come round, unless I have a massive fish with a big stack on my right, because you can't play “drawing hands” when the effective stack is 40bb.
Other players will buy-in for 80c but play atrociously, stacking off pre with A7s or pocket fours. These guys are donators; it's just unfortunate that they only have 40bb to give you and not more! The loose/bad short-stackers are probably recreational players on a budget. They will see how long they can make their stack last before quitting for the night, so you often see them sitting with a pitiful stack of 13c or so. It's quite funny when they wake up with aces and only make 13c of profit when I put them all in. I don't mind seeing these guys on my table, as I can still play hands like ATs and KJs for top pair value against them, but I'd much rather they were playing 35/4 with a full 100bb buy-in. Hands like 55-22 and 76s have little value in a pot with these guys, unless the hand is multiway.
Exploiting short-stackers: Don't play small pairs or suited connectors in pots with SS-ers. You don't have the implied odds. Play “top pair” hands and get committed on the flop/turn if you hit. If you get into a raising war pre-flop, stack off QQ+/AK against a SS in EP/MP, and add JJ and AQs to your stack-off range if you and the SS are in LP or the blinds. You have to take flips with short-stackers to get maximum value from them, and just deal with the variance when you run bad. You can steal blinds from tight shorties (treat them like nits and use 2.5bb for your button opens) but the loose SS-ers are much more stationy and will call your steals much more often.

Next week, I'll post a short blog about seat-selection, for those situations where you find a good-looking table with a two or three available seats, and I'll also give you information on how to tell when a table has gone “bad” to the point where it's no longer worth sticking around. After that, I think we'll be ready to get stuck into post-flop play with the long-awaited article on continuation betting.
Questions, comments and suggestions are as welcome as ever on my blog thread in the forum.

Till the next time, I hope you find the juiciest fish and keep winning their chips!