Sure, you can just tap your friend on the shoulder to wake them up when they're supposed to be helping you with the taxes or homework, but it's much more fun to throw scalding tea in their face or attach several clothespins to their face. Usually we'll see this sort of stuff in anime -- an episode of Ichigo Mashimaro had the girls repeatedly hitting each other with a fan in order to keep themselves awake.
How do you keep your friends awake? Or, do you just draw on them mercilessly for being the first ones to fall asleep. Note to the Japanator staff: I am off-limits to these pranks when it comes to Otakon. Unless you want to try and find a place to sleep in the Baltimore Convention Center.
I had "baka" drawn on my forehead once when I fell asleep during a long late-night marathon panel. I didn't even notice until I woke up and got in the elevator which had mirrors.
But seriously, you're missing all the good ones where they REALLY wake people up. >D
http://www.youtube.com/watch?v=MrEPt79QQQI