Doc's name, credential (M.D. or D.O.), specialty, # of hours you shadowed. No one expects you to be doing procedures - that's why it's called shadowing. Adcoms just want to know that you have been exposed to the reality of medical practice.
A couple of tips, based on things I have seen this year while serving on the adcom at my medical school:
1. Try to shadow more than one specialty.
2. Try to ensure that one of the specialties you shadow involves primary care.
3. Only report shadowing with an M.D. or D.O. While it may be interesting to shadow a psychologist, a podiatrist, a chiropractor, or a veterinarian 😕 (I have seen people report all of these as "physician shadowing"), don't list it on your application. We're not going to count it, and it looks like you're trying to pad your application.
4. Make sure you spell the doctor's first and last name correctly. At least where I'm at, many of the in-state applicants end up shadowing docs in the same community where the medical school is located. Unsurprisingly, in many cases someone on the adcom knows the doc the applicant shadowed -- and recognizes that the name is spelled incorrectly. This makes you look sloppy and careless, which is probably not what you're hoping to get across.