correct bluffing frequencies on flop/turn/river ip and oop

[donkeykong2]

well the obvious answer to this post could be: "it depends" like basicly everything in poker. so as an assumption i assume an opponent with decent skills comparable to yours not a donkey you can fool into believing you have tons of great hands which will make him fold all the time nor the other donkey who will call you down every time although you havent shown any bluffing tendencies at all.
i think the easiest street to determine the correct bluffing frequency is the river. if you make a pot sized bet it should be at 2-1 (value, bluff). but what about the other streets? What about the difference between in and out of position? Can anyone come up with good stuff and a solid game theoretical argument for it? [img]/images/graemlins/wink.gif[/img]
thanks in advance!