Oh, good job! You must be excited, judging by your posting name 🙂
Anyway, make sure he knows you're really interested in it and ask him at the beginning if he'll sort of explain things as he goes along. Also, try to schedule different days of the week to shadow. I've found that doctors seem to do the same types of things on the same days. If you spend different days with him, you'll get to see more of what he does. Try to see surgery if you can!
Also, out of courtesy to the patients, you might want to face the other way for some stuff. When I shadowed a colorectal surgeon, I always turned around when he did the rectal exams. It seemed like the nice thing to do, lol.