Assuming you're getting enough sleep, I've found that one has two areas to address--mind and body. Keeping your mind engaged in something interesting/exciting/fun helps keep me from "drifting" (the prelude to lights out!). The other thing is physical change in circumstances from what you're currently in provides some boost
For example, if you're sitting, try standing. If the room is dark, try getting in the light. As Lemon suggested, if it's warm, try cooling off. Just slight changes (even slightly changing positions can help). Just beware that if you go from one to the other, make sure it has to be of equal or less comfort than what you're moving from. If you go to more comfortable, you'll just get more sleepy! (I know from experience!)
Hope you're able to find something useful. Good luck!
BTW, trying to stay awake when you actually need sleep can really be painful (I tried staying up as many hours as possible once just to see how many I could do--it actually hurt after ~30 hours--not recommended!)