When to Check

First of all, if a maniac is playing behind you, that is a perfect opportunity to check. These people generally bluff with the same precision and focus as somebody trying to kill a mouse with a hand grenade. In short, they bluff for the sake of bluffing. If you bet, they are simply going to call and probably raise anyway, so why should you do the heavy lifting? Let them do the betting. Your check also lends further anonymity to your hand, and helps make it more difficult for them to put you on a hand.