Easy: Don't fall asleep.
Actually I find it easiest if I keep myself occupied with activities, that take active mental thinking, such as doing chores, playing certain kinds of video-games, walking around, and even exercising. Caffeine and the ilk will keep you going for a little but, but then you have that crash and suddenly your bed looks like the best thing ever. You could also try movies like other suggested, but that means you're basically sitting down for an hour or two which doesn't help in keeping yourself from falling alseep, so make sure its a loud, action packed movie.
Jam it back in, in the dark.