During the flight, try to plan meals and sleep around the expected destination times. Drink plenty of water, try to exercise and avoid taking too much alcohol. Make yourself comfortable by wearing loose-fitting clothes and perhaps bringing an eye mask and ear plugs to help you sleep. On arrival, stimulate your body to the new time by eating and sleeping at the relevant local times. Exercise helps, and light walking is ideal.
Many travellers report that exposure to sunlight after arrival also aids synchronisation.
The medical world is looking at specialised hormones to ease jet lag, but this is still highly experimental. One promising development is stimulation by intense light pulses during the flight. This appears to rapidly synchronise the brain to the new time zone.