and is not intended to be a comprehensive list.
Don't buy the cheap plastic neck pillow, get a good one with fabric covering.
Bring bottled water. Not just *a* bottle of water, bring 3-4. Planes are very very dry.
Take a shot of Nyquill or Benadrill, before and 1/2 way through the trip, helps your sinuses and helps you sleep.
I know it tough coming down to the wire as you prepare and pack for the trip, but be well rested before you even start.
As tempting as it is, don't take a nap or "brief" lay down during your arrival day. Force yourself to make it to at least 10pm, before heading off to bed.
Just in case you can't sleep, bring books, games, cards, spare charged batteries for gameboy and/or computer.
Don't drink alcohol before or during the flight. Avoid fizzy drinks.
Bring some munchies, power bars and your own favorite drinks. The carts don't come by often enough or they don't have what you want/need. I drink diet ginger ale on planes (which violates the previous tip, but helps me with other issues.)