What do virgins at the Rocky Horror Show forced to do?

runtheatrerun asked:

Me and my friends are thinking about going to see a live showing of the Rocky Horror Picture show, but heard that first timers (virgins) are forced to go onstage and do stuff. We are unsure if we wanna go for fear out of what they might make us do. So if you could tell me what they have to do that would be great. I'm pretty sure we are going no matter what, we just want to know.