Before you leave – Get a good night sleep before you fly, or at least try to sleep before you leave for the airport.
Adjust your watch – Adjust your watch to the local time while you are still on the plane.
Drink – Drink lots and lot of water.
Alcohol and Coffee – It is best to avoid alcohol and caffeine while traveling. Alcohol and coffee dehydrate the body, which makes jet lag worse.
Exercise -
walk up and down the aisle
It is a good idea stretch your arms, legs and neck
squeeze a ball or something the size of a ball to exercise your arms
circle your feet
Meals – While traveling try to eat meals as close to the local time of the final destination as possible.
Eat light food throughout your travels.
salad
fruit
yogurt
rice
Sleep – Sleep as close to the time at your final destination as possible. If it is daytime at your final destination, try to stay awake as much as possible, even if that means staying awake on the plane.
Tips for sleeping on the plane
bring with you some soft socks
a pillow
a blanket that is good for flying
earplugs
a blindfold
change your clothes to something more like night clothes
shorts and tee shirt
training pants and sweet shirt
Shower – Take a shower as soon as you arrive at your destination, and if possable in between flight.
In between flights take a shower if possable.
Wash your face, brush your teeth
Change your clothes
Final Destination -
If you arrive at your final destation during daylight, then try to spend some time outside in the sunlight.
Activitys – Try to take a day or two to get reajusted. Try to plan high energy activities what you think you will have the most energy.
Medications – Ask your doctor what is the best way to take medications.

Don’t drink much coffee or alcohol. Don’t be tempted to watch the in-flight entertainment the whole time, try and sleep during “lights out”.

You are trying to give your body a “normal day” but with the pressurization, you must keep up the fluids to keep your body hydrated because the environment is so dry.

Be aware that if you have pain in your leg/s up to a couple of weeks after flying, get to the doctor as soon as possible and make them check you for deep vein thrombosis.

ps: I take an EMPTY water bottle onto the plane with me then fill it up on one of my walks. (You are not allowed to take the bottle if it has any liquid in it at all.)

If your body is hydrated and rested, you will settle into the new routine much quicker.

A few days before your flight, start going to bed later than usual, adding an hour or two each night. As the above people said, drink lots of water.

When you get there, immediately adapt to the new time. Seek light and stay up until bedtime there. Exercise during the day.