Time management skills are essential to office practice, and can be a very valuable lesson for the student. Teaching in the exam room is an efficient technique. While you are examining the patient, explain what you are doing and why. Describe your differential, what is likely and what isn't. This teaches both the student and the patient.
Patients also enjoy being a partner in the teaching process.
Literature study is an important part of the preceptorship. They learn, and often you will too. Importantly, you are teaching the student that they can't know everything, so they must be comfortable identifying and using medical information resources. An added benefit is that by sending the student to the literature, it gives you a chance to catch up on patients. Present it to your office staff or even the hospital staff.