I've had a couple friends tryout at BYU and Utah. They tell me that open tryouts are really just about measurables. Coaches are looking for a certain height, weight, and speed. Generally, they don't care if the kid can catch, throw or kick--my buddy that tried out as a wide receiver was never asked to catch a pass, run a route, or block anyone. The coaches were just looking for a body for the scout team--someone who moves fast and will give the real players a look.