A bluff is a bet or raise with a hand you do not think is the best hand. With more cards to come, you should generally restrict yourself to semi-bluffs with hands that may become the best hand. When deciding whether to make a pure bluff, you estimate whether your chances of getting away with it are better than the pot odds you are getting. However, if there are more cards to come and you plan to continue to bluff, you must take into account your effective odds.
On the end you should usually bluff with a busted hand when you think your opponent is weak. Against a tough player, the bluff tends to work more often in first position. However, if you have a hand with some value, don’t bet when you are first so that you can snap off your opponent’s bluffs. If you are in second position and your opponent checks, show down these same hands since they have little chance of winning if you bet and get called.
The odds against a bluffs working increase almost geometrically with each extra person in a pot. Therefore, it is rarely correct to try to bluff out two or more players, especially on the end. When to bluff and when to bet a fair hand for value is a difficult problem of judgment and experience. In general, if you do not think you could get away with a bluff, you should bet your fair hands for value; if a fair hand cannot be a profitable bet, then a bluff should be.