Today I will be succinct.

1. Use a poker tracker. If you don't have one, get one.
2. After compiling  a number of hands, go to hand flag.
3. Sort by winnings in BBs
4. See what hands are costing you BBs. You will be surprised.
5. Write down those hands. Tape it where you can see it when playing.
6. Those are your leaks. Huge warning bells go off when those hands are dealt to you.
7. Analysis what you think is going wrong with those hands
8. Play those hands differently based on your analysis
9. Watch your over all EV rate increase.

Thats is all.