Slowplaying

There's often a temptation to disguise the strength of your hand by refusing to bet with a strong holding. Checking with a very strong hand in order to hide the fact that you have a big hand is known as slowplaying.

Weak players tend to slowplay far too often. Since they tend to play passively to begin with, other observant players will assume they're quite strong when they do decide to bet; that then encourages weak players to continue playing passively even with strong hands, so that they can extract more from their opponents. For aggressive players, this is unnecessary; since they often bet with weak or marginal hands, they can safely bet when they make a strong hand as well.

So, when should a good player slowplay? It comes down to getting a feel for what your opponents might hold. If you hit a board very hard, but you believe that it's very likely that your opponents haven't improved, you may wish to give them a free card -- provided it's not likely that the free card will allow them to beat you. This way, your opponents might improve to a good (but second-best) hand, and be willing to put in a few extra bets they wouldn't have if you were initially aggressive on the flop. On the other hand, if you believe your opponents are likely to have improved -- for instance, if you hold 77 on a board of AQ7 -- then it's almost always better to bet rather than to risk losing bets by slowplaying.