Set your watch to the time zone at your destination and try to get on the same schedule. This might mean sleeping in-flight and eating dinner when you think it should be time for breakfast, but it will help your jetlag and allow you to adjust faster to your new surroundings upon arrival.
Watch the stretching videos provided in your in-flight entertainment and learn proper methods for stretching while sitting down. Walk around the cabin for 10 minutes every few hours to avoid deep vein thrombosis, a condition brought on by extended periods of sitting.
The length of long-haul flights can cause severe dehydration, so be sure to drink water regularly and keep alcohol consumption to a minimum.
Don't wait until arrival to fill out the landing card and customs declaration. Filling it out when the flight attendants bring it by is the best way ensure you'll get to the front of the immigration line.
