regimen
Like a lot of the other guys, I'll use earplugs and eye shades and agree that window is preferable to aisle. Comfy clothes too, and change into your business attire at the other end if you need to.
I also take a valerian tablet about 30 minutes before I want to rest. It's herbal so no bad chemicals or groginess on arrival, that coupled with a glass of wine and I'm usually set for a good 3-4 hours sleep even on a coach seat.
Out of curiosity I've wondered about those neck pillow things, has anyone got any thoughts on their usefulness?