You asked about neck pillows. They are really dorky looking but who cares? I find they keep my neck stable and a little more comfortable. You can also do a search and find lots of info & reviews on Flyer Talk about neck pillows.

Bring a large, warm scarf-pashmina kind of thing. They fold up really small in your carry on and it is an extra layer of warmth around your shoulders.

I've heard that a window seat is best for sleeping so that you can lean your pillow and head against the cabin wall. I like the aisle seat because I hate feeling fenced in and want to be able to get up without distrurbing others. So take all that into consideration when booking your flight.

Don't drink coffee all day the day of your flight. I'll just have my 1 morning cup the day of a night time international flight. Also watch those other caffeine sources like some sodas, chocolate, etc.

Have a great flight!