At my old college, "squatters" have first pick. If you want to keep your room, then you have an entire day to squat in it through the main system. If you don't squat in that time period (a little less than a full day), then you may or may not get to keep your room. Honors and disability students have first pick after that. Then seniors, juniors, sophomores, and freshmen have periods of time (like a week, I think?) to choose their rooms. Freshmen are segmented into three groups via the alphabet (randomly ordered), so any given freshman may have to try to get a room in a different, better building a full three or more weeks after room registration starts. I kept the same room as long as possible, personally. It was like having a home away from home--there's a certain sense of comfort to have "your" room on campus.