A great ratio to use is called the "M-Ratio." Below is the link to the Wiki page for it which has a great chart relating how you should act depending on how deep your stack is. If you use a Heads-Up Display (ie. Poker Copilot, PokerTracker, etc.) you can have these automatically spit out these numbers easily at all times during MTT's (for you and everyone else).

NOTE: Moderators - I hope it is not against the rules to post outbound links. If it is, I am sorry and do apologize. Just please let me know for the future :)
http://en.wikipedia.org/wiki/M-ratio

In addition to the "M-ratio," an easier way to calculate when to shove pre and judge your plays accordingly is to look at how many BB's your stack has. While the M-Ratio will help you be more accurate in your decisions, the BB calculation is easier and takes less time. (Generally, it's accepted if you have anything <10BB left, you can shove pre with a premium hand.)

Other than that, take into account how your opponents are playing. If they're playing loose, play the tighter hands and also a few of the SC/drawing hands. If you make your draw, it'll be an easy way to double up yourself while stacking them.

Alter you play based upon the style of play of the others on your table.
Pay particular attention to how many bb's in your stack and knowing what this means (eg. with a 15-20bb stack we will actually need to tighten up our range of hands we want to open with but at the same time this is a very good stack to implement re-steal shoves with < picking the right spots is the key).