First of all, congrats on your desire to shadow! It is a great opportunity to view different fields and jobs in medicine. By no means should you feel you need to be an expert or know everything about the diseases or medications you might see. Shadowing is an opportunity to learn about the environment, you are not expected to see patients on your own so you should not expect to be quizzed. When you ask people if you can shadow them, let them know you want to learn more about the field and day to day life of a doctor. It is a great opportunity to ask the doctor you work with about his or her training and education, or even why they choose that speciality. When shadowing, be sure to be polite, arrive on time, and be respectful of the patients and office staff. When I was in college, I shadowed at a podiatry office and with a pediatrician. The shadowing opportunity turned into a summer job for me, it was great to get paid while continuing to learn! If you shadow with someone for a few months, they might be a great source of a recommendation for college or medical school.