There is wisdom in many paths...

- Often the theory is to not sleep on the flight, to essentially be awake, land and stay up no matter what until natural night and then sleep.
- But generally I sleep on the plane no matter what (sleeping pills) and then take more of them when I need to sleep that first night (midnight local Tokyo time).

I find the second option to be best, it makes the flight go by quicker and ultimately gets me on Tokyo time faster. I've lately dialed down the Ambien (it did strange things.. read: unexplained scars and burns, yeah, don't get me started) and so I've opted for over the counter sleeping aids and melatonin.

Anyhow, despite your drug of choice, I'd recommend you NOT stay up all night and try to get on local time ASAP if you are staying for 3 days or longer. If it's a short stay, screw it, just stay up all night every night and sleep in the day.