1. Beater is good.

2. If not 1, electrician's tape for concealment is good.

3. When I was in school, some organized bike thieves would come to campus with trucks during spring break or christmas break and steal a lot of bikes then. So even if you normally leave your bike locked outside, make sure to keep it in your room during holidays.

4. Like dobber said, try to see how much actual bike theft there is on your campus/in the town. While $150 in locks is never the wrong answer, exactly, it's often overkill for those numerous locations where pretty much only unlocked bikes are ever stolen.

5. But sometimes people will steal saddles or wheels with QRs more as an act of vandalism than because there is any real value to a used seat. (Remind me again...why do saddles even have QRs?).