Same as what the dude above me said. In early position, if the blinds are big and/or there are likely raises behind me.....I'll fold. Late position, if somebody has raised a considerable amount, I'll fold. Late position, no one has raised, I will limp in to try to see a flop to get trips. Pretty standard stuff there.

Shorthanded play I may take a stab with these, though, depending on other players of course. Shorthanded and shortstacked I'm going all in pre flop to either a) take the blinds, or b) go heads up with somebody in a coin flip.