If traveling east, start going to bed and getting up earlier. Consider taking prescription or homeopathic medications. Get plenty of rest. As soon as you've boarded the plane, set your watch to your destination's local time and immediately begin to adjust yourself to it. Drink plenty of fluids, especially water.
Dehydration can make jet lag worse.
Avoid alcohol or caffeine at least three to four hours before bedtime. Both act as stimulants and prevent sleep. Avoid heavy meals. Wear earplugs and blindfolds while sleeping to dampen noise and block out unwanted light. Staying indoors can make jet lag worse, so try to get outside in the sunlight whenever possible.