If you are to succeed in no limit Texas Holdem or any form of poker, you must understand value betting. Most bets in poker are made to force players with marginal hands or draws out or to build pots. A value bet is a bet that you always want called, but you rarely want raised. It is a bet you make when you have a hand that you are fairly sure is best, and you would like to earn some extra chips with it. When should you value bet?
Value betting is a Texas Hold em strategy that primarily comes into play on the river. If you think you have the best of it earlier in the hand, you often want to make a large bet to force out draws, or to define your hand. On the river, when there are no more cards to come, you can decide whether you think you are best and bet accordingly. Let's say you have T J and see a flop of A T 4 rainbow. You bet and are called. The turn is a 9, you bet and get another call from one player. Another T comes on the river. This is a good opportunity for value betting. If you check here, an opponent with an ace will probably check along, especially if their kicker is weak. If you move all in, you may get called by a player who suspects you are bluffing, but in all likelihood, a wide range of hands that you beat that would call a smaller bet will be folded to an all in.
In this situation, you need to calculate the maximum amount a player will call and bet that amount for value. A bet of half the pot is often a good value bet, but it will depend on your read of the opponent and your image. With the right sized bet, an opponent with any ace may suspect that you are trying to buy the pot with the scare card and will call you. If you are raised all in, you may have to worry that you are up against a hand like AA, A T or 9 T, but this will happen infrequently, and you will have bet little enough that you can get away from the hand if you are sure you are beaten.
A common situation where it is not profitable to value bet on the river is if a card comes that either made your opponent's hand or missed him entirely. In this situation, your opponent will fold if they missed and raise you if they hit, so there is no benefit to raising. As you gain experience and learn how to play Texas Hold 'Em, you will be come much more proficient at distinguishing these situations from real value betting opportunities, and your win expectation will grow accordingly.