I always found that one way to minimize jet lag is do NOT take a "nap" when you arrive at your destiniation. Do your best to drudge through the day and go to bed at a normal (or maybe a tad early) hour. Then, when I wake up the next morning, I'm fine.
You'll have to fight this the most on the U.S. to Europe flights where you leave in the evening and arrive in the morning, not so fresh and ready to begin your first day of sightseeing. It helps if you don't schedule sedentary things like museums on day one...do walks, stay outside where the fresh air will help keep you awake.
I am not the greatest on sleeping on planes, but if you can get even a bit, it helps. Take earplugs and one of those banditto masks to put over your eyes. You'd be amazed out how they help block out that your sitting uncomfortably amongst hundreds people.
Oh, and I've read that it is best to stay away from alcohol and caffeine while inflight. However, I've found one or two glasses of wine after they serve dinner on the flight can put me out...no getting hammered, though!