[Daithi]

teddy,

I agree with Ignatius. Here are a couple exceptions.

PRE-FLOP
Either limp, bring in for 3xBB, or raise 2xPot when limiting field of limpers.

If there is enough money in the pot I like to move all-in with AA and KK. Sometimes I move all-in with AK as well.

In tournaments, when the blinds start getting up there, an all-in bet with any Ace and a relatively short stack is another nice play.

If you have been stealing the blinds alot and someone pops you back with a raise then I also may consider moving all-in (I'd have to have any Ace or a pair in my hand).

FLOP
If I have a monster and I am bet into I may move all-in.

Likewise, if I have something like 2nd pair and the nut flush draw and someone bets into me I'll move it all-in. (Credit to FossilMan).

In a tournament I may have raised and gotten called pre-flop. If I have already commited a substantial part of my stack I may move all-in regardless of whether I hit the flop or or not (technically I think this falls under Ignatius' 40% rule).

There are exceptions to the exceptions as well. If the money is really deep I may not move all-in but would be willing to over bet the pot instead (but I would not over bet the pot in a consistant manner).