When you arrive at your departure airport set your watch to your destination time.
Sleep as much as you want to on the flight.
Wear headphones to avoid being woken - listen to some smooth tunes on your MP3.
Take snacks and bottled water.
Don't eat big meals before and during your flight.
Take a puzzle book to keep your mind active while you are awake.
Take a pee long before they put the seat belt sign on for landing.
(Waiting too long in line for Immigration when you're busting makes you bad tempered)