Most thefts can be prevented by properly securing the bicycle with an adequate lock, to a secure parking facility such as a bike rack. U-locks, such as Kryptonite, are recommended, but a knowledgeable thief can easily defeat even these. A 6-foot cable or chain (the thicker the better) used with a U-lock allows you to lock to any rack and secure your wheels as well.
Be aware that any cable is easily cut. Don't entrust your good bicycle to a cable alone. Most bike thefts on campus are due to "cut" cable locks.
When parking your bike, don't obstruct walkways, railings, doorways or ramps intended for use by pedestrians or people with disabilities. Improperly parked bikes will be removed and impounded by Stanford Public Safety. Utilize bicycle racks whenever possible.