Mash keys very quickly for as long as possible. It actually gives your forearms a killer burn... play it when ya wanna impress the ladies.
I'm still learning Flash, and this is my first game, which I kinda pumped out as an experiment... so don't hate me :) All you have to do in this game is type... really really fast for a long long time. Your forearms will burn but you're gonna have to push through it if you wanna place on the highscores. Best of luck...