I think you will find that it varies widely place-to-place. When I shadowed, I was allow to watch most exams (as long as there wasn't too many people in the room or the animal wasn't dangerous) and all surgeries. I also was allowed to set up but not read fecals (although they'd show me if they found anything interesting), clean, and probably on occasion do other things if they were short handed (fill prescriptions, run UA sticks, start blood centrifuging, etc.) But all this showed that I was interested and hard working enough to get hired on. 🙂