When your stack gets under 10 BB's...
A lot of players misplay hands when they have a short stack, mainly by not being aggressive when they pick up a hand.
When your stack is under 10 BB's, the only moves you should be making regularly, are going all-in or folding. A case can be made for calling with some hands like small pcoket pairs when you have a stack 9-12 BB's...
There is a reason that you should not be making standard raises when you have this short of a stack (0-10 BB's). The reason is if you make a standard 3-4x the BB raise, you are commiting yourself to the pot. If someone calls your raise, the pot will usually at least be the size of your remaining stack, therefore very valuable to you. Most of the time if you make these standard raises and are called, your money is going in later anyways.
If you are re-raised after you make your standard 3-4x BB raise, you are getting the odds
to call anyways, so moving all-in instead of raising 3-4x BB is a move that gives you more fold equity.
Fold equity deals with the odds you are giving your opponents to call you. If you make a larger all-in bet, the odds for your opponents to call go down significantly where if you made a 3-4x BB bet, your opponents odds would be better.
Basically, by pushing all-in with a short stack, you are giving your opponent a bigger reason to fold, even if he may have you beat (without his knowing of course). Putting a lot of chips in the middle and forcing other players to make tough decisions is more effective and profitable than simply raising and possibly getting called, and then be faced with a tough post-flop decision.
Here's an example of what I am trying to illustrate.
Big Multi-Table Tournament
1200 started, 135 cash, there are 60 remaining.
Blinds are 1000/2000 with an ante of 100. 8 players are at your table
Relevent stack sizes for this hand: (after posting blinds and antes)
CO (you) 18,000
It's folded to MP2 who calls the BB of 2000.
It'd then folded to you, and you look down at 88.
Raising to 8,000 here would commit almost half of your stack, so you would be commiting yourself to the hand if you made this play.
Folding is an option if you feel you are beat, but one limp ahead of you tells
me that you very well may have the best hand here.
You look at the stacks behind you and see that everyone has you covered, but you can do significant damage to each of their stack's if you go all-in, they call, and they lose.
Let's say for example you decide to raise to 8000. It's folded back around to MP2, who calls.
Now, you have 10,000 chips left and there are 19,800 chips in the pot(8,000 (your raise) +800 (antes) +3,000 (blinds) +8,000 (his call of your raise)).
The flop comes KJ5 rainbow. He bets 10,000 to put you all-in. You would be getting almost 3:1 odds to call here, and you have to wonder if he has hit a K or J or is bluffing with a hand like AT, AQ, 66 or something like that. A difficult decision arises with this standard raise play. Most of the time if you see a flop with this hand, there is going to be at least one overcard.
Now, let's say you decide to push your remaining 18,000 into the pot after MP2 limps. If the button, SB, and BB want to call, they would be putting in large portions of their stacks. In the case of the SB and BB, it would take at least half of their stack to call. The BB may have a hand like A9s, but will decline to call even though he is only a slight underdog to win the hand (although he doesn't know it).
Let's say it gets folded back around to MP2, who now has a dillema. He holds a hand like ATo, KJs, or a small pocket pair. It will cost him 16,000 chips to make a call and win a pot of 23,800. If he calls and loses, his stack will decrease by 1/3. Your opponent may decide to throw away a hand like AT or KJ here fearing being dominated by AK,AQ,KQ, or a big pocket pair. If you had simply raises to 8,000, he would have only had to call 6,000 and many players will make that call given good odds (6,000 into a pot of 13,800 or over 2:1 odds).
By raising all-in instead of standard raising in a situation like this, you are giving your opponents a stronger argument for folding, hence you have more fold equity on your move of all-in.
There are cases in which a standard raise would be a good play since you want to generate some action. This should only be used with hands like AA or KK in certain circumstances. Observant opponents will know you have a good hand if you have previously been pushing, and all of the sudden you standard raise.
I hope this post gives some insight into solid short stack play.