The thing that works for me is to stay up through the night, all the way until I'm due to go to bed (as an early bird). That way, even though it's early, I'm really tired and can sleep. After that, force yourself to get out of bed when the alarm goes (even though you'll still feel dog-tired for the first few days). Eventually, your body will get the hang of it. Just don't let yourself drift: it's ridiculously easy to just start going to bed later and later and, before you know it, you're a night owl again.
Start having a light supper at 10 pm. Then go shower. Then get straight in your bed and go to sleep. Does that sound boring? It's the best, most unworkable advice you will get ... and it will only be unworkable because IF you aren't prepared to change your rest-pattern you aren't going to change anything.
Why not? This is something I had to do. Forget the cicrumstances, I HAD to do this. Not sleeping for a few nights whilst putting in a few days tired me off my feet until, after not too long, I couldn't wait to fall in bed and started sleeping like a top. It worked for me ... it had to do and I had no other choice!
I'm the other way around so I had to get a hobby to really get into to keep me up at night.
I only meant once just to put you on the right track or try this-> Try and stay up for a whole day and then sleep the next when you want to start sleeping again. Then just stay on that pattern.