1. Don`t skimp on tickets. If you spend that long in a flying tin can at least the food and service should be excellent.
2. Try to arrive in the late afternoon or evening. Depending on the airport, the queues at immigration/passport control will be ok.
3. Get an electronic passport which allowes you to go through the automatic passport control. Saves soo much time!
4. Re-hydrate: Always ask for seconds when they hand out thimbles of drinks. Makes you feel better and you will have to get up for regular trips to the bathroom. Which will help prevent thrombosis.
5. Avoid caffein and alcohol at high altidude.
6. Nap whenever you can.
7. Never and I repeat never travel without earplugs!
8. Choose your seat asap according to your requirements. Mine is to be able to get up whenever I want to. Unfortunately you can`t take amazing pictures from the aisle seat.