Situational Studies in Poker
If you read books about poker, they dictate that there are categories of cards to play, and that you play the situations that arise out of those cards. The top is the primo cards like A-A, K-K. It scales down through lower pairs and high connectors (A-K offsuit, K-Q offsuit, and so on to mid pairs, Ace-X cards, and so on. If you stringely follow the suggestions on the card, you'll be in pretty disciplined shape for any situation.
Here are a few suggestions for what you're likely to face after the flop:
The Nuts: You're holding Ah-Qh and the flop comes Kh-8h-2h. In possession of the nut flush, you want to entice other players to bet, setting a trap to pay off your hand handsomely. Now, you may have raised pre-flop with that A-Q suited and made other players wary. In early position, you should check this situation and then just call (after suitable "thinking" time) any bet presented. Now you're set up to take what you can after the turn and river.
Great-But-Beatable Hand: A strong pair in your hand (Jh-Jd, for example, always flatters to deceive, and loses so often it's uncanny) is facing a 10s-8s-7d board. Someone with pocket spades puts you up against a killer flush. A J-9 gives a straight, and you're sitting on an inside-straight draw. Time to make a mark and push people out, particularly if you're in late position and no one has bet.
Second Best: It happens so often, it's a crucial situation to study. You're holding As-Jc in early position. The flop comes Qs-Jd-2c. Second pair with a strong kicker feels good, but that Q looms large. It's a tough one to fold, but if you're facing down a big bet (from a tight player), then his representing the Q should be good enough for you to fold. If you call, prepare for a long-haul turn and river as you chase a draw to hit an Ace or another Jack.
Draw: Ad-Kd is tough to give up even when faced with a 6h-3c-2d board (though the low cards could mean all the other players missed, too), but that 2d sends shivers of a runner-runner nut flush draw down your spine! Your decision here should be math-based. Essentially, what are your pot odds? How many outs do you have, and what kind of bet are you facing? Following the things that you've learned from poker books, you should work out exactly where you stand with the pot odds and make a mechanical statistical decision, that helps remove the emotional attachment you get to strong starting hands that are undercut by challenging flops.
Junk/Trouble: You saw the flop with your pair of lucky 7s and they look decidedly dodgy against a flop of K-J-10. You'll lose a lot of money chasing that set, so lay them down quietly to the first bet, and forget you ever saw them. On to the next hand!