In poker, it is important to consider what your opponent has put you on. Your opponents read on your hand will ultimately influence their approach to the hand.
Understanding what your opponent's put you on serves two purposes. First, it can save you money when you're behind. Second, it can help you gain bets when you're in front and your opponent puts you on the wrong hand.
Let's start with saving bets. I have AK. I raise before the flop and an opponent calls me. The flop is A-9-7. I bet, this opponent raises, I reraise and he calls. The turn is a 5. I bet again and he raises me. Dealing with this raise on the turn is now to be regarded as the most critical point in the hand. If you call, you absolutely must call the river no matter what falls (2 big bets). If you fold, you may save two bets if behind, but you may also cost yourself the pot if you have the best hand. Reraising is an option, but it seems dangerous because your opponent is representing a very strong hand. This is a situation where you have to draw on a complex line of thinking or psychology. You have to consider what you think your opponent thinks you have. I know it's a bit of a knot. But it's not that difficult in application. Of course, this applies to games where your opponents are fairly experienced and/or fairly good.
On the flop I raised, so my opponent probably gives me credit for a reasonably good hand. When the flop came ace high, I bet, he raised and I reraised. Now my opponent is fairly sure that I have either AK or AQ. What's more, my opponent knows that if I have AK or AQ, I will bet the turn automatically if he calls me reraise on the flop. As such, he calls and then raises me on the turn. The long and the short of it is: he can beat my hand. He would have two pair at a minimum and knows full well he is in front of my AK.
This is a very important aspect of hold'em. You must be thinking about what your opponents put you on (what hand they think you've got). It clearly figures in their decision making process as most reasonable players won't raise if they are somewhat confident that they're in front on you. The exception, of course, is when they have the nuts. In that case, it's irrelevant what you have. As such, if you have been playing your hand obviously and an opponent starts raising you, you should think about whether they are raising because they know what you have and can beat that.
Now let's look at the occasions where you can make money with this technique. Let's say an opponent raises before the flop and you call with 9-9. The flop comes Q-9-3. Your opponent bets and you call, intending to raise on the turn. On the turn, an ace falls. Your opponent bets, you raise and then your opponent reraises. At this point, you usually get this shallow empty feeling because you think your opponent has AA or QQ. But I recommend that you relax and just concentrate on what you think your opponent put you on.
On the flop, he bet and you called. This indicates to him that you didn't really have much of a hand on the flop. On the turn, an ace falls. He bets and you raise. In this case, he probably put you on ace-high on the flop and a pair of aces on the turn. More often than not, this player will probably have AQ or maybe AK if they make loose raises. It is very rare to have a set over a set in a hand. So in my opinion, you should consider that your opponent has put you on a weaker hand than you have which is why they reraised you on the turn. Since he would have put you on the wrong hand and your hand is stronger than the one he put you on, it's time to raise.
So when confronted by a raise, especially when you hold a relatively strong hand, ask yourself this:
(a) what would your opponent probably put you on? AND
(b) Is this answer to (a) correct or close to correct?
If the answer to (b) is yes, consider folding. If the answer to (b) is no, consider reraising if your opponent has probably put you on a weaker hand than you actually have. (See also best review poker online)
However, if you're bluffing, the answer to (b) is no, but your hand is weaker than he thinks. As such, a fold is in order. Let's say you are in a middle position and there are two players before you and one player behind you. The flop comes Q-8-3. I have J-10. On the flop, the two players before me check. I decide that they didn't hit that flop (based on a number of considerations) and I decide to bluff, hoping the player behind me didn't hit that flop either. While I do have a gut-shot straight draw, I am not really semi-bluffing as I don't really have enough outs. Unfortunately, the opponent behind me calls and two before me fold. On the turn, a rag falls and I bluff again. Again, my opponent calls. What do you do on the river? It depends on the player. But if I am up against a standard player (who plays fairly tight before the flop and has reasonable understanding of the game), I generally won't bluff on the river.
In this situation, my opponent would think that I have a pair of queens or A-8 (middle pair with a good kicker), especially when I bet the turn. He knows I'm not semi-bluffing because there doesn't appear to be any sort of opened straight or flush draw on the flop. Since he is calling, he thinks he has a reasonable chance of beating my hand in a showdown, but doesn't want to raise in case I have A-Q or K-Q. I'd say he has a queen with a half decent kicker – perhaps a 10 or a Jack. There is no point in me bluffing again on the river, because my opponent already thinks that I have a pair of eights or queens. Most importantly, I cannot change his mind about the hand I'm representing by betting on the river. Of course, if a 9 falls on the river