In poker it's not only what's in your hand that counts, but also what people think is in your hand. If you bet as though you have better cards than you actually do this is called bluffing, yet the true skill is knowing when to bluff. A player who never bluffs cannot expect to win as much money as someone who bluffs with the proper frequency, most average players tend to bluff too much, particularly in limit games. When bluffing at the proper frequency not only do you gain by forcing opponents to fold winning hands but also you create an element of disguise with your legitimate hands.
Optimum Bluffing Frequency
David Sklansky (p.166 Theory of Poker, 1999) describes the optimum bluffing frequency; when it makes it impossible for your opponents to know whether to call or fold. Mathematically, optimal bluffing strategy is to bluff in such a way that the chances against your bluffing are identical to the pot odds your opponent getting. Thus, if your opponent is getting 6-1 from the pot, the chances against your bluffing should be 6-1. Then that opponent would break even on the last bet by calling every time and also by folding every time. The mathematically optimal bluffing strategy isn't necessarily the best strategy; it is much better if you are able to judge when to try a bluff and when not to in order to show a bigger overall profit
As you will find there are good times to bluff and bad times but here are a few simple rules that should help you along your way:
Bluff bad/loose players. Bad players don't necessarily know when they are beaten. So even though you may present yourself as having the stronger hand, they simply may not notice or may not care.
Don't expect bluffs to work in low limit Hold'em. If the cost to see your cards is not significant, why should your bet (or raise) keep anyone from paying to see them?
Try to bluff many players. You may fool some of them, but if you don't fool everyone you are in trouble.
Bluff when the board says "someone" might have made a monster hand. An example is when the third of a suit hits the board. "Someone" might have a flush. If you bet as if you have the flush, the other players may believe you do.
Bluff against good or tight players. If you are in a pot with a player that looks for a reason to fold, give them one. Try betting big and making them think you have something they cannot beat.
Bluffing is something that is done between players, so the more you know your opponent's habits the better. If a player is a 'calling station' and always calls bet so they can get to the next card or see the showdown, don't bother trying to bluff them.
If players have caught you bluffing recently, they will remember it. If you try to bluff again too soon do not be surprised if someone calls you, just to 'keep you honest'. Of course this can be used to your advantage. If you find yourself with good cards right after being caught bluffing, you are more likely to have players call your bets, rewarding you with a bigger pot.
Some circumstances have risen as 'typical' bluffing situations. They can be used to your advantage, but veteran players may recognize the play and use it against you. Typical bluffs include:
Sitting in late position pre-flop. Everyone folds before you. You then bet big, knowing that there are only two players competing against you and that they didn't bet because they liked their hand. They bet because they had to. The players may interpret your big bet as a sign of strength and simply fold. You will have "stolen the blinds".
Betting big from last position after everyone else has checked. You can interpret their checks as a lack of confidence in their cards. They may interpret your bet as a strong hand and fold.
Bluffing is an art, and it spices up the game of poker. Make bluffing a part of your arsenal, but not your only weapon at the poker table.
For more information on bluffing check out Matt Lessinger's Book of Bluffs
Here's an example of a great bluff by Robert Varkonyi in the 2003 WSOP Main Event