There's only one way to be absolutely certain of avoiding the ill-effects of long-haul travel: don't go.
If, however, you simply must fly, there are some steps you can take to ease the passage.
*The first, of course, is to go first class. Which isn't much use for those of us for whom turning left as you board the plane is a pipe dream.
*The best-value technique I've found involves a sleeping pill, one of those cushioned neck rests and a small bottle or two of complimentary red wine. The neck rest is the key.
As much as boffins and spoilsports recommend avoiding grog at altitude because of the risks of dehydration, I'm generally pretty excited to be airborne so, at 10,000m, I can usually be found seated behind a drink. And then perhaps another.