Early Stages

In terms of strategy, no-limit tournaments are very different from no-limit ring games. You simply can't bluff as much because people's stacks tend to be smaller in relation to the size of the pot. Also, since the amount of chips you win from a bluff is worth less than the amount you stand to lose, bluffing loses a lot of 'value.'

Now, many of you may be confused. Suppose you bluff 1,000 chips at a 1,000 pot and figure you have a 50-60% chance of taking it down. Many of you would think it's worth it to take that risk. However, those 1,000 chips you win are worth less than those 1,000 chips you stand to lose. If you have a 2,000 stack, getting knocked down to 1,000 has much more negative value than the positive value of getting up to 3,000. The 1,000 chips do not represent money. The only monetary value in the tournament is either losing all of your chips or winning them all (and losing them all is more important because you do get a prize if you lose them all in the late stages of the tournament). Losing those 1,000 chips knocks you half the way out, but winning those 1,000 doesn't do squat for winning.

This is not to imply that you can simply fold your way into the money. The blinds will eat you alive. You must win pots so you don't get knocked out most of the time. Towards the end of the tournament, you can think of winning pots to win the whole tournament. However, most of the time you must win pots simply so you don't lose!

Thus, in the early stages of the tournament, you should avoid gambling much. Generally, the amount you win isn't worth the gamble. If you can see the flop for cheap with a suited connector or someone goes all-in preflop and you have [[cards As Ah]], by all means go for it. However, I wouldn't suggest bluffing all-in. In the early stages, you want to win a huge pot here and there because you hold the nuts. Target a bad player and make him pay you off.

Middle Stages

Towards the middle of the tournament, you need to switch gears. Since the blinds get bigger, stealing the blinds will help you stay alive. Here, the 'gap' concept becomes more important. It takes a much weaker hand than usual to raise to steal the blind, but a stronger hand than usual to call a raise. The middle rounds introduce the 'survival mode' concept.

Again, most of the time you will be looking just to survive and increase your stack bit by bit in the middle rounds. You want to avoid confrontation without the nuts and just take down some small pots without controversy.

However, if you are a large chip stack (or even just a medium one), you may want to take advantage of this survival mode. Take control of the game by raising and frequently putting other people at a decision for all of their chips. After all, if they go all-in, they're risking it all but you aren't because you can lose the pot and still keep on fighting. However, don't do this too much. Steal some pots, but don't be so obvious that people will call you all-in with top or even second pair. Also, don't do this against very bad players. They will call everything.

End Stages

Towards the end of the tournament is when the coin-flip decisions become very important. Frequently, the blinds are so high it makes sense for a player with a low or moderate stack to go all-in preflop. Generally, when you go all-in you want to have Ace and good kicker or a pocket pair. If you have Ace and good kicker you are an advantage against all unpaired hands and may even have someone dominated. If you have a pocket pair, you are a small advantage against all unpaired hands and at a huge advantage or disadvantage against other pocket pairs (depending on who has the bigger one).

Generally, if you have one of these marginal hands, it's best to just shove all of your chips in preflop. When you are a low stack, you cannot afford to be blinded away anymore. Once the flop comes, chances are it's not going to be perfect. By shoving in all of your chips preflop, you have the added chance of stealing the blinds and can avoid being bluffed out.

Taken from pokertips.org (contributed to blog by Skinski)