Well, it's easier to set the mood. One thing is to have a sleepover (under the rationalization of studying for a final, SAT, or equally life-altering test) and start talking about girls you like or watching something sexy. (In the 90s, the show of choice was Baywatch.) When he says he has to go jack off, you're in. Say that you have to too, and since there's only one bathroom and you're both guys . . . (Note: This method requires that one, you both have similar classes, and two, you only have one bathroom.)

As an adult, porn's probably the easiest way to set it up.