i used to think that going all in was sure to get a player to fold almost instantly, not so much any more. in terms of pre-flop, if i have pocket aces, regardless of position, i will threebet all-in, or at least raise 5BB. Other than that, you are just setting yourself up for a fall.  as far as post flop goes, regardless of cards or position i will never shove on the flop, partly because there is always some player that knows you're bluffing, and partly because if you think you are ahead then you should hand over pot control by checking. A shove on the river is a delicate thing. If someone has put out a large bet when you have the nuts, then shoving should be the only thing on your mind. if you are trying to bluff someone out of a pot, you might as well send them a message telling them that. usually a half or three-quarter pot sized bet will do