When deciding whether to bet or check you should always take into consideration what you think your opponent thinks you have. If you know your opponent beleives you have a strong hand then you can obviously bet him out even if you have a weak hand. If your opponent thinks you have a certain hand, you can get him to lay down any hand that's worst than the one you beleive he's put you on.

Though if you know your opponent thinks your weak and you are, trying to bluff is a very bad strategy. He'll reraise you 90% of the time unless he's playing scared then you might have an easier time getting him to lay his hand down. Though if you are reading your opponent to be putting you on a bad hand when you have a monster feel free to bet. You will most likely get a raise. The best strategy when he raises you is to call. This will completely throw him off. He won't know if you have a monster, a draw, or nothing and you are looking to steal it next round.

Always think about what your opponent is thinking. Remember it's a lot easier to know what they're thinking when you are in position.