How can I make myself cry hysterically?

I have a really important role in one of my school's plays, and in one of my scenes I have to cry hysterically. I want to do a really good job since this is my first play. Is there any way I can do this? Don't tell me to think about something sad because that usually doesn't work for me. No onions or anything like that either, that won't make it hysterical.