I was going to respond with what we do until I saw Marlese's response below - and she does everything exactly the way we do it. Nothing left to say. :) We've been on over 30 flights with my 2 year-old, and these are the things that work for us. Just remember - try to really think about what he will need on the plane, and for the lag time getting baggage, etc. right after the flight. Otherwise, don't lug yourself down with a ton of extra stuff that you might use - bring the essentials and it will be so much easier when you're rifling though the bag to get your license at security or his snacks on the plane.
I always do a new toy on the plane too. It doesn't have to be anything extravagant, just something new. That always buys you some time.
Also don't bring out your tricks (new toy, DVD player) too soon on the plane. Space them out, and fill time in between looking at the trucks and planes out the window before takeoff, or reading stories. This will keep him from getting overstimulated too. My son is fascinated with the window pull shade, the tray table, etc. Good luck and you will be fine! Oh also, ignore anyone that shoots you a dirty look for having the gall to bring a baby on the plane. My son, who is a total spaz half the time at home, is a pure angel on the plane and I still get dirty looks sometimes if he makes any noise. Some people have apparently forgotten that they were 2 once!