Pending on redeye flight length; 6 hours vs 12 hours vs 19 hours. Also if you are seating coach vs business; the recommendations and strategy will change.
Keep in mind that airline travel is at its worse; most airlines have moved into a lean/lean model with commoditizing basic comforts into an up-charge. This with most flights being 100% booked, empty seats are rare.
1. On the longer flights take a layover and then buy a united club pass (or another brand) for the airport lounge; aim for 3-4 hours to relax and de-stress.
2. Do whatever you can to hack a business class fare; sign up for their credit card and use miles+money – typically my goto (if you don’t have any FF miles). Buy upgrade at airport day of the flight (risky). Check FF forums in other ways.
3. If business class is a “no-go”; st the very least grab an exit row seat; although most of the scumbag airlines are moving this to an economy+ seat and no longer give away for free.
4. Headphones; grab a pair of in-ear; fairly high-end; Shure is my favorite brand. Over-ear headphones (Bose) are bad for long flights; they bruise ear/soar, you cannot easily sleep with them on and snag while sleeping and will wake you up. The in-ear soft ones that expand are the best and can be worn for extended lengths with little discomfort.
5. Dress for comfort, and make sure you solve both hot and cold temperatures; there seems to be 0 control over what the flight attendants set for a temp; some flights are freezing; others are like being on the sun; have noticed that exit row tends to leak cold air in through the door.
6. Have multiple media sources; typically I go with, a. kindle b. audiobooks c. music d. movies on tablets; have a giant cellphone battery for backup to above for the longer 12hours+ flights. Besides the music; relaxing nature sounds are great for sleeping and drowning out the horrors of air travel.
7. Thick socks or slippers; personally I can’t sleep with shoes on; but on colder flights, you end up freezing your tootsies off.
8. DO NOT sit anywhere near the bathroom!!! People congregate there throughout the entire flight and will keep you up; not to mention the smell on the +12 hour flights can start to become unpleasant.
9. Misc: Big bottle of water; toothpaste, toothbrush, other freshen-up bathroom supplies.
10. Get on a flight early so you can stuff your carry-on in overhead and save your foot space; unpack essentials into your seat pocket or have a mini bag to put under your seat (I store a mini bag inside my carry-on). Some airlines now charge for carry-on or only allow 1; keep that in mind if you go this route.