Like Piers with the limit section I saw the void in the MTT section and decided to add a first post. I have nowhere near the expertise Piers has, so this is meant more to inspire discussion than to instruct. Also note, posts like this one tend to write themselves at the expense of a logical progression. Let me know what you agree/disagree with, what you like and what just plain confuses you. Lets get this forum started right!
It's easy to find a book or forum discussion about solid MTT play. Going into the tournament you should feel good, have a good idea of how to adjust your play. The point where that always seems to break down for me revolves around scope.
What do I mean by that? In an online tourney it's very easy to look at your standing compared to the chip leaders/small stacks. In a live tourney a quick glance around will get you the same comparison. While this information is useful and can help you judge when and how to change gears, you must be very careful not to put too much stock into it. Especially early in a tournament.
Likewise, rises and dips in your own stack must be looked at in the correct perspective. Don't create artificial goals ("I want to get to 3500 by the first break" or "If I drop to 500 then..."), that will put undue pressure on your play. Until you get down to the critical stack size (5-10BB) or a fairly significant chip lead you should not change your strategy greatly based on changes to your stack alone.
My greatest successes in MTT's have come when I focus on the hand being played. For me, the times when I look or plan too far ahead (or too often) are the times when I make mistakes. You will not survive deep into tournaments if you don't take stock and adjust, but don't overdo it and outplay yourself either. Remember, what it all comes down to is playing good poker, and in order to do that you have to buckle down and pay attention to the hands being played.