That's true in theory, but in my experience it doesn't work that way in practice. Having done more than my fair share of long-haul flights, I have arrived at the definite opinion that one should sleep when one can. I do usually set my watch to the destination time shortly after take-off, but then I just "go with the flow" as far as sleeping goes. I get much more sleep that way than if I try to time my sleeping according to where I'm going.

Beyond that, dress comfortably; take a good book or two, ones that you will enjoy reading and that are easy to put down and pick up again; enjoy the in-flight entertainment or your iPod or whatever (and I do like my noise-cancelling earphones on long flights); go easy on the alcohol; and drink plenty of water.