in NL cash games at low limits you're going to be wrong about whether someone is bluffing the majority of the time, its not worth trying to make the miracle call. Once you get up to like 100-200NL you can worry more about that. In SNG's, people do bluff a good amount of the time. But, my overall advice for bluffing, is you yourself should never bluff in a cash game, only bluff near the end of sng's, and only call what you think is a bluff once in a blue moon: don't force it, wait until you are extra positive its a bluff, not one of those times where you think its possible.