I have been on many a long flight, some of the longest including:
Newark direct to Hawaii (with kids!!)
Newark to LAX to New Zealand
Newark to LAX to Tahiti
Phila to Rio
Phila to Turkey
A few things. Don't get stressed out trying to sleep. You will be excited, so at first you won't want to sleep. Try to keep to a regular routine. I try to stay up maybe an hour later thasn usual, and wakeup and hour earlier. This way I am a little bit more tired, but not over tired. Sometimes that overtired thing backfires, and then when you get on the plane you can't sleep.
Next, noise cancelling headphone--the best thing ever created. Buy them!!! They will stop all the ambient noise, and the hum from the plane. Even when I don't have them plugged into the flight audio, I leave the switch on and it stops all that ambient noise.
Eye mask. Yes, it tricks your body into thinking its night, and it does help you sleep.
A nice glass of wine wth dinner is great to relax you.
Something to read.
Try to upgrade if you can. Review your airlines poilicy on udgrades. It may not be as costly as you think. We have high status on a few airlines. so thankfully all of our long flights have either been in business or first, where you have either a lower recline or the seat turns into a bed (omg thatis the best). I like this because after my glass of wine, I go with two benadryl. I lower that seat down, pop on my eye mask and headphones (yes, go visual it is an intersting sight), and off I go to sleep. My husband has the gift of just closing his eyes, and going to sleep. I don't
I hope this helps.