How to Play NL Hold 'em With a Large Stack

If you're sitting at a NL table with a large stack, then you're sitting in an ideal position to say the least. The strategy you choose should consider two things: 1) how to protect and grow your stack, and 2) how to use your stack. Players considering only the first issue may play too conservatively and by the final table may find that what they considered to be a large stack is now the smallest. On the other hand, players using their large stacks to fund over aggressive betting may lose their stack to reckless playing. The best strategy is one that covers both issues.
The great thing about a large stack, whether you're in the early rounds or at the final table, is that it gives you options. In the early rounds, you can literally afford to fold. You can likewise afford to hold out for monster hands and can pick and choose your hands based on the best pot odds. In the middle rounds, you should still be playing tight-aggressive, but you can now use your stack to steal the more sizable blinds. You've got the chips necessary to take more risks. You can bluff and semi-bluff without worrying about contention, and will likely be seeing many more showdowns.
If you're sitting in the later rounds with a large stack, then it's time to flex your betting muscles. You know the short-stacked players are biding their time between blinds hoping to get the chance to choose their big hand. Wherever possible, push these players. If they go all in and you have a good hand, remember that you are wagering just a fraction of your stack for the opportunity to take theirs and move up one place in the tournament.
On the other hand, avoid playing overly aggressively with calling stations in the later rounds. Their playing style makes it almost impossible to know what they're holding, and in many cases they are eager to go all-in to try to double their stack. If however you know your hand is strong, don't be afraid to use your stack to overbet. By the final table, the blinds are high enough to justify this kind of playing. A calling station will only sweeten the pot, though by now the other players are tightening up and will more likely than not fold.
The biggest advantage of a big stack in a no-limit Hold 'em tournament is that you have the power not only to call your own shots but to start manipulating others' too.