I have just come back from the USA and had to endure a 24 hours journey ( actual travel time of over 16 hours) to do so. It's great to be back home, but coping with jet-lag is always hard to do. I am a poor traveller, but interestingly, this time the jet-lag has been much less. The reason was simple - I just slept through the flight.I napped as much as I could during the flight. The result is that I have now bounced back to normal much sooner than I would have !
It's important to be well-equipped, and to get on the flight with the intention of sleeping through it. This can be hard to do, because airlines keep on plying you with food and drinks to entertain you. It's useful to be well-equipped. Carry your own snacks, so you can eat when you get up, not when they want to feed you ! I found the sleep mask from The Body Shoppe extremely useful - it effectively blocks out all ambient light so you can concentrate on sleeping !
There are now many audio tracks which will help you to sleep, and it's a good idea to carry your own music ( using an Ipod or a walkman) to do so. This helps to block out the ambient sound. I wish the airlines would offer a sleep audio channel to help their passengers sleep well during the flight, so they can get up fresh and well-rested !