[Snarf]

At an aggressive table I bet out enough to make anything but a king fold.

At a more passive table...

Slansky talks about it...if your hand is likely to
a) not improve to the best hand if its already beat
b) not be outdrawn if its currently the best hand

Then he reccomends 'slowplaying'

You get more value from lesser hands while not losing more to the hands that beat you.