Just dont bust out early with unimproved AA or KK. That would be GAY.
On a more serious note, read all the books you can on Tournament strategy. I've heard Championship NLHE by Mcevoy and Cloutier is a good one and harrinton on holdem is prolly the best.
Focus. Dont drink while you are there. You need your mind sharp, remember is a shot at 7-10million bucks!, not to mention the glory
. If you find yourself earlier in a table full of rocks, steal lots of pots and prepare to fold to any resistance. Dont bluff EVER at the early stages of the tournament. If you put all you r chips in, it'd better be a good hand.
At the early stages, there will be lots of people busting out with bad hands, it is important not to want to take part with marginal hands, since a bad beat is more likely if you are holding, for example, 8-6, in a 8-6-3 board vs. KK.
I havent participated in a huge tournament. I am not a good tournament player but those are some guidelines I took from a post by Johnny Chan on his forums. They all sound pretty logical to me...