I work nights but don't do a set shift as such. I work for a film company and deal with film shot in production that day. So depending on the shoot day (when they wrap, how long the lab takes to process it etc.) depends on when I start. We've just started a new project and normally I start around 1am. Good news is that I can go once we've done our work so a lot of the time I'm out on the first tube home (~6am). When they start shooting more though that will obviously change.
I didn't actually find it as hard to adjust to nights as I thought I would. Personally I keep my meals at the same time as they would be on days and I think that helps immensely. I can't think of anything worse for your body than trying to have your 'dinner' at 4am

So I have some cereal when I get up, then have dinner with the girlfriend about 8pm-ish. I'll then have a sandwich or something small at work about 4-5am, then as soon as I get home I can collapse straight into bed. Like others said, if you're in bed at 6-8am you can still get your quota of sleep and have an afternoon to yourself.
After a Friday night at work I'd get into bed asap, then sleep for maximum 5hrs. Hopefully will be up by midday Saturday and then I'd be tired enough to sleep that night. The benefit of that is you get a Saturday afternoon and a full Sunday. I'd tend to sleep in until 11am-ish on Monday morning to catch up on the sleep missed on Friday night, then I'd have most of Monday which is nice, then in at night and back into the nights routine. Not too bad, really.
The main thing I would recommend is eating your meals at their usual time. Makes the swap-over so much easier! The main problem with nights is just missing out on a social life. It's hard to want to get up, go out and meet friends and then have to go to work
