Agree with Renee.
The best mechanism is to try and get some shuteye on the flight, and the best way of achieving that is either to fly out at nighttime … or limit the amount of sleep that you have the day before you leave.
Flying business class will help your chances of sleeping, and I always find that a nice cheeseboard for dessert followed by a couple of glasses of really good port (not that aussie muck) is helpful for dozing off too.
Also this class usualy has good in flight entertainment, news, and individual films (with over 50 to choose from) so they pretty much cover your waking entertainment.
IF you are in cattle class, then it’s tougher. Get a window seat so you’re not bothered on both sides, or by people getting up.
Try and get a seat right at the front of the cabin partitions (where there is no seat in front) as that at least allows you to stretch out a bit and not sleep like a pretzel. Also bring an inflatable neck pillow, otherwise you’ll regret it when you wake up.