Theoc-
It depends on exactly what it is you want to learn, and what level of proficiency you want to achieve. I enjoy doing complete physical exams, so that was my starting point. I watched a lot of videos, I already knew how to auscultate and assess vital signs. A real life MD from this site was kind enough to share his teaching protocol for physical exams with me, and that was a huge help.
I had never done reflex testing or palpation on a human, but being a vet tech, I've done plenty of that on animals. Again, videos and nursing manuals were a big help. At the end of the day, attitude and atmosphere are most important. If you want to create a realistic scene, a good grasp of terminology is vital and so is a professional demeanor.
As for some of the procedures and treatments; if you're going to do anything invasive (sounding, catheters, etc.), learn aseptic technique and take it seriously. Bear in mind always that you are not out to hurt your patient, the purpose here is to fulfill their fantasies, and yours. A little discomfort is part of the medfet genre, intentional pain is not.
It's been said many times before, but it bears repetition; play safe, play sane, play consensually!
Play On!
LadyDoc