Staying well hydrated is a must.
This might just be me, but I'd recommend taking more than one form of entertainment - e.g. take something to read/watch, and something to listen to. I usually start with a magazine, but I find that the dry air on long flights makes my eyes feel scratchy after a while, and I just want to lie back and shut them; but if I can't sleep, I go crazy with boredom if I don't have podcasts or music.
I hope you enjoy yourself when you get there.