Thanks techman and beatlesfan.
Techman, do you mean that those jobs are assigned based on their best evaluators and they will call/email you if they want you to do it?
beatlesfan, thats what I thought. I have only signed up with about 20 so I guess I have a lot of signing up in front of me. Luckily, I live in a very large city so I think I will have a lot of opportunities if I find them and they like my work.