So a specific answer is:
If you leave near Wettersteinplatz, I used to go to Dr. Cesar Perez. I was always happy with his advise and was always in a good mood. They don't give appointments, or at least they didn't, so if you go 15 min before they open in the morning you'll always be the first and you'll be done without waiting time. If you go at around opening time, the cue will be 10 people, and you'll probably wait for longer than 1,5h.
I go to another one now just because I moved.