1)Buy a pair of Bose QuietComfort 2 headphones. They'll run you $299 direct from Bose and are well worth the investment. You will be amazed at how much less stressed you feel when you have pleasant white noise in your ear instead of loud engine/air/cabin noise that just gets to you after a while. Plus, your movies and audio will sound much better.

2) Avoid the 747 in coach where you can in favor of the 777. The latter is much more spacious, both in terms of leg room and seat width.

3) Drink plenty of water.

4) Sleep. If you deliberately do not sleep the night before, then make sure you that you do sleep a lot on the flight. Otherwise, you will be a colossal wreck upon arrival. And that applies no matter which class of service you're flying.

Happy travels!