The Stack Size

The size of your chip stack is a very important factor in poker tournaments. For example, it greatly influences the way you should apply the gap concept.

Small stack
If you're stack is small the gap decreases. In these cases you can't afford to risk chips by steal raising with average or weak cards. However, you should keep in mind that a paradox exists here that opens up plenty of opportunity for reverse psychology. Since you have a small stack, your opponents will be less inclined to call or re-raise you if they're not holding very good cards.

This reason for this is the fact that they know you are not as likely to be bluffing with a small stack, and they will be reluctant to gamble against you with weaker cards since there is not much for them to gain. Therefore, your chances of making successful bluffs actually increase in situations like this. On the other hand, a player with a big stack might take this (rather small) risk in order to knock you out of the tournament. Your ability to read your opponents correctly is really tested at times like this.

Medium stack
Playing with a medium sized stack is actually much more difficult. When you have a medium sized stack you're forced to make a number of tricky decisions - you are trying to increase your stack to a big one but, at the same time, trying to avoid becoming short-stacked. Your poker skills are really tested in these situations. Generally, you should play more hands against the smaller stacks and avoid the bigger ones.

Big stack
Your stack is your primary weapon in a poker tournament and when it's big you have every chance of dominating the game. However, you must keep in mind that the other players will be expecting you to play more aggressively and will try to trap you in the hopes of doubling up. You should play aggressively but not carelessly. When you're stack is large, the gap gets bigger and you will be able to take more risks. Use your stack to put pressure on the other players by betting, raising and re-raising. But as mentioned, you should not get reckless. If you do, you will take unnecessary hits and might suddenly find yourself with a medium or small sized stack.

Source: WSOP