I've given myself some rules so I don't go overboard staying up late, like not doing anything work related after 3am or computer games after a certain time. When I don't follow these I generally get up later and later until I'm on a truly unworkable schedule. I find it's pretty easy to go to bed a little later each day, it's much harder to go to bed earlier, at least for me.

The other solution is to plan stuff early in the morning.