Again, it depends on your college. At my college, they don't really focus on bringing in stage managers. I wasn't offered a scholarship until a performer dropped his about two weeks before the semester. And I know they've bypassed stage managers for performers in the past.
At my interview, which happened at a professor's house and was probably the most awkward interview I've ever been in, I didn't have a single thing. I should have had a resume at least. That's all he asked for. But I had no idea. Going to college wasn't even in my plans until my high school teacher (bless her!) called the then department chair and told him he had to schedule an interview with me. Now, during the recruitment period in the spring, they ask for at least a prompt book and a resume.
As far as stage managing for the department... If you want to ASM, you generally can. It's a season of 9-10 shows so we need 18-24 ASMs. If you want to stage manage, you have to have taken the Stage Management class, ASMed, had an informal interview with the RSM (me), and then be cleared by the department chair and the director. We don't require anymore experience than that, since we need so many, have two, and are kind of desperate.