The no meals thing/only sleep thing works for 10 hour flights but not for 20+ (Europe/US - Australia). For really long haul flights, do all of what he said, but

The no meals thing/only sleep thing works for 10 hour flights but not for 20+ (Europe/US - Australia). For really long haul flights, do all of what he said, but only at "night time", i.e., when they dim the lights for you to sleep. Eat and drink (water only, and drink a lot of it, you'll need the excuse of going to the bathroom to get off your butt and walk around on the plane and get the circulation going a bit, also it's easy to get dehydrated on long haul flights) whenever it's offered, though you can probably miss snacks if you're sleeping. I always end up tired when I arrive, but I've usually had close to 10-12 hrs sleep at various points on the plane trip, so I've "had" enough sleep, it's just the exhaustion of the actual travel and jet lag. Then the biggest thing for jet lag is, keep busy for the rest of the day and go to bed "normally", i.e. when it's the actual time to go to bed in the new place; usually that'll kick the jet lag pretty quickly.