Continuation bet size and optimal frequency?

I generally make continuation bets of half the pot. Is it wise to vary the amount some times?
Also, I go on judgement when to make the bet but is there a mathematical optimium frequency such as the game theory approach used in Theory of poker?
I tend to make the bets when i'm out of position rather than in position, where I sometimes take the free card and if it's no help I might make a continuation bet on the turn.
Would like to hear your thoughts.

[lautzutao]

I'd like to know when you DON'T make continuation bets of half the pot. Do you only bet more than half of the pot when you have a big hand? Do you bet less(or check it) if you miss the flop or hit a draw?

I don't think you ever want to do one action in a particular situation all the time...someone is going to pick up on it eventually and punish you for it. As to how much you vary it I'm afraid I don't really know.

a continuation bet is supposed to look the same as hitting the flop. ask yourself what you would do if you hit your hand (top pair, top kicker for example). if you typically put in a pot sized bet in this situation then your half pot continuation bets will get run over by an observant player. i would recommend not making a continuation bet unless you feel that your opponent will lay it down.