I probably overbet more than most and normally do it in one of three situations:
1. I flop a nutted hand on a wet board v. a thinking player who will put me on a bluff. See this hand for instance, where I shoved over a PFR's c-bet with a made straight on a two flush board.
http://forumserver.twoplustwo.com/17...89/?highlight=
2. I'm semi-bluffing against a capped range.
3. I have the super nuts (or a very strong hand) against a player that has a nutted hand that is inelastic to sizing. For instance, I have AT on an AAT55 board, and V leads into me. He either has Ax and will call whatever I bet, or he doesn't and is probably folding no matter what.