I fly from Germany to the states about once or twice a year and its always boring. A few tips :

1.Bring lots of reading material; both books and magazines you can just flip through
2.Try to sleep as much as possible. Ear plugs and a eye visor can help
3.Watch the movie if you can't sleep
4.Chat with your neighbor if he or she is friendly
5.If you want to stand up and streach alot get an aisle seat so you can get out easliy. If you think you will be able to sleep, get a window so that your neighbor doesn't have to wake you to get up.
6.Make sure you bring a sweat shirt or something else warm. It will be hard to sleep if you are cold.
7.Bring a few of your own snacks
8. Audio Books on your IPOD and/or CD player. I used to use this one for long solo car rides and you get caught in the story and time goes by quicker. You can get audio books on cd from most local libraries which you can then rip to MP3 on your computer and then transfer to your IPOD or other MP3 player. Comedians standup routines are also good.

I know most of these are nothing new, but those are my 2 cents. Good luck.