i reckon postflop play doesn't get nearly enough attention in most poker books or websites. as dunk said there is plenty of info out there for preflop strategy, but not postflop.. especially concerning the nl game rather than the limit game. here are some things that i've discovered that are handy for navigating those more tricky situations where its unclear. most of these apply to the shorthanded game which is the game i've probably spent the most time playing..

you call a raise from a loose aggressive player with a pocket pair and the flop comes low cards.. overbet the pot because he probably has high cards and hasn't paired the board. you don't want him drawing

with a paired board like 669 or QQ7.. if you're in a multiway pot in a full ring game, someone probably will have the trip, whether its high or low. however shorthanded, usually if the trip is low there is a higher chance that people don't have it, since shorthanded, people normally play hands with either one or both high cards. if you're pretty sure no one has the trip, you can normally bluff people off the pot.

if you hold a pair like 88 99 or 1010 and you're faced with a raise from a tight player and you're not sure whether he has unpaired high cards or a high pocket pair, you can normally get a better read on him if you just call his bet and hope the flop comes low cards. sometimes you will hit your set and get paid off big!

raising in late position with any two cards: i normally only do this against players i know will fold on the flop if they have nothing, ie tight players. if they call you on the flop normally this is a sign they have hit and you can back off. i normally use this move occasionally to keep my scoreboard ticking over, because its an obvious move, and if you do it too much people will start to call you down. against tricky players sometimes its worth doing this when you hold a nice preflop starting hand and try and rinse them for money when you hit. i've actually found that raising in first position is better for stealing the blinds, because people haven't actually put money into the pot yet except for the blinds, so they don't feel they've lost anything if they don't call. it also looks like you have a stronger hand if you do it.. lots of people will put you on KK or AA if you're raising in first position and will just fold even if they hold a nice hand.