Some players — and it's only a few of them, to be sure — never bluff. After you figure out who they are, playing against them is easy. If they bet once all the cards are out, you can safely throw your hand away unless you believe that your hand is superior to theirs. If it is, you should raise.
Other people are habitual bluffers. When they bet, you have to call as long as you are holding any reasonable hand. Although habitual bluffers will also make real hands every now and then, the fact that they bluff far too often makes your decision easy. By calling, you'll win far more money in the long run than you would save by folding.
Keep 'em guessing
No easy answer exists concerning players who bluff some, but not all, of the time. Opponents who bluff some of the time are better poker players than those found at either end of the bluffing spectrum. Better players, of course, can keep you guessing about whether or not they are bluffing. And when you're forced to guess, you will be wrong some of the time. That's just the way it is.
Of course, you may be able to pick up a tell (a revealing gesture) and know when your opponent is bluffing, but that's not too likely in most cases. The sad truth is that players who keep you guessing are going to give you much more trouble than predictable opponents.
In most low-limit games, players bluff much too often. After all, when you play fixed-limit poker, all it costs is one additional bet to see someone's hand. And the pots are usually big enough, relative to the size of a bet, to make calling the right decision.
Here's an example: Suppose the pot contains $90, and your opponent makes a $10 bet. That pot now contains $100, and the cost of your call is only $10. Even if you figure your opponent to be bluffing only one time in ten, you should call. By calling, the laws of probability suggest that you'd lose a $10 bet nine times, for a loss of $90. Although you'd win only once, that pot would be worth $100. After ten such occurrences, you'd show a net profit of $10. As a result, you could say that regardless of the outcome of any particular hand, each call was worth one dollar to you.
The threat of bluffing
The threat of a bluff is just as important as a bluff itself. A good player — one who bluffs neither too often nor too infrequently, and seems to do so under the right conditions — has something else going for her, too. It's the threat of a bluff. Does she have the goods or is she bluffing? How can you tell? If you can't, how do you know what to do when she bets?
These answers don't come easily, and even top-notch players are not going to have a terrific batting average in most cases. As a result, the threat of a bluff combined with the bluff itself, is designed to help a player win some pots that she would otherwise lose and to win more money in pots where she actually has the best hand.
After all, if you have the best hand and come out betting, your opponent won't always know whether you're bluffing or not. If a lot of money is in the pot, she'll probably call. That's the less costly error. After all, if she were to throw the winning hand away and relinquish a big pot, that's a much more costly faux pas than calling one additional bet.
Bluffing and the threat of bluffing go hand in hand. A bluff can enable a player to win a pot she figured to lose if the hands were shown down. The threat of a bluff enables a player with a good hand to win more money than she would if her opponent knew she never bluffed.