When you become the short stack it's most of the times the best thing to shove all in with several hands and the shorter you become, the more hands you should shove. Some people define short stack as 10BB or less, others at 15BB or even 20BB. I keep myself somewhere around 15BB.
The reason for this is that you can win the pot by making everyone fold. If you have around 10BB and everyone folds, you steal the blinds which is, if ante is play and in a full ring of 9 people, 2.4 or 24% of your stack. This is a good amount of chipping up. The other possibility is that someone calls you and you have the chance of doubling up and be in a comfortable position again.
The range of hands you should be open shoving with as a small stack depend on your position (later position means a wider range) goes from high and medium pairs, high aces, medium suited aces and 2 face cards. If your stack gets smaller or your position later you should also include all pocket pairs, suited aces, medium suited kings and medium suited connectors. If it becomes really small and you're in late position, you can also include all kings, a lot of suited queens and jacks and maybe even suited tens.
Of course when you see someone is shoving all the time with a big stack, you can call him with a medium A or K, but there's always a risk that you're losing a big stack, while the blinds are small, so I prefer to wait till I have a real hand and be almost sure that I get his stack.
The shoving that you talk about with AQ is a decent play being a small stack, for the reason that most of the time you will be ahead or it's a coinflip (if the other person has a pocket pair lower than JJ). So you win either by everyone folding or you go against someone having the advantage (or coinflip). Over the long term you win with this.
This in contrast with 22, in which a coin flip is the best case scenario, while with AK or AQ, it is the worst case.
Originally Posted by drcarloshimg
2. Preflop with AA, KK
I suppose you mean as a short stack, because as a big stack you're most likely have everyone fold and you're only stealing the blinds, while with those hands, you should get at least a caller and build the pot over the streets, until the next card could become dangerous and then you can bet big to make him fold.