I used to work for a long-haul airline and gave presentations on this topic all the time.
Let's see how much I remember!
- get yourself a blow up neck pillow and eyeshades. They work great for long flights where you cannot lay down.
- Try to get yourself a window seat. You can lean against the window. Only downside is you have to crawl over two people to get to the restroom
- Most likely you are taking a night flight across the Pacific. If this is the case you'll probably be fed dinner shortly after takeoff. Try to eat something as it will be a long time before you get fed again. If you enjoy a drink, have one (only one!) now. After dinner, they will mostly likely put on a movie or two. Try to relax and sleep at this time. If you are comfortable with this idea, take a over the counter sleep aid. I found this helped me to fall asleep.
- Try to get up every once and awhile to walk around (if this is allowed) and stretch. If not do small exercises while in your seat. Move you feet up and down, bend over in your seat and touch your toes, small butt crunches, anything to get your blood circulating.
- Bring a large bottle of water on the plane. Drink lots of water. Try to stay away from soft drinks, alcohol and coffee. Keep hydrated. You'll feel much better upon arrival.
- if you cannot sleep, bring a good book to read.
- try not to bring a huge carryon, or try to leave the area under the seat in front of you open. This is good for stretching your legs.
- I always brought my portible CD player and my music. I found it relaxed me to have my own CD/tapes.
One other piece of advise. If you arrive in HK in the morning try not to go to sleep right away. It will be hard but you should try to not go to sleep until after dinner. Have a light meal and then an early bedtime. You'll wake up refreshed the next morning, and shouldn't suffer too much jet lag. If on the other hand you go to sleep, your body clock will be all messed up and it'll take a few days to recoup.
Have a great trip!!