I'm trying to get to sleep, and failing miserably, so I guess I have the opposite problem to everyone else here... (Yay for insomnia!)
As for deliberately staying awake, the only way to manage it is to find anything to occupy your time until you feel you should sleep. Films, TV series (better, as you have to be awake to change things more often), puzzles, games... anything that keeps your mind going for a while. Books are bad though - it's quite easy to fall asleep whilst reading. Caffeine sort of works, but it doesn't make you any less tired, it just keeps you awake - mental stimulation can stop you from feeling tired, at least temporarily.