If you want the reality of medicine, I would make sure your Health care shadowing/volunteering experiences are in a hospital. If you can do it in a hospital in an academic medical center that has an attached medical school with it, that’s even better, bc you’ll see medical students and residents and see what they do. See if you are really comfortable with seeing patients who are very ill and sick, dying cancer patients, angry patients, watch a CODE BLUE being done, doctors trying their best with IV lines and tubes and patients still dying, ICU medical care, etc. If you see those type of scenarios you’re much more likely to see the reality of medicine as it is, not how you want it to be. You’ll be doing a lot of this as resident - working very long hours, with little sleep, and paid a very measly salary - $40-50 K, while all your other friends have normal lives. You’ll get a small taste of this as a Year 5.
Private practice medicine will never give you a realistic picture of what medicine is like in medical school and in residency, bc most rotations and residency usually happen in an inpatient hospital setting where people are admitted, not in an outpatient clinic. Only certain specialties are as a rule practiced largely on an outpatient basis: Allergy, Dermatology, Pain medicine (fellowship), Psychiatry, etc. I understand though it can be hard as only a high school student to get that opportunity.
You can definitely google more about this topic, but more and more specialties in medicine are being practiced in hospitals as teams, and not just teams of physicians only: http://www.ucsf.edu/news/2014/08/116856/team-based-approach-primary-care
http://www.amednews.com/article/20120319/profession/303199952/2/
You’ll have to work in a group with nurses, NPs, PAs, social workers, physical therapists, etc. and many times you will be responsible for them as well (which can be frustrating, as you’ll realize that there are lazy people in healthcare who don’t care as much as you do for patients) as well as to your patient. If you talk to older doctors, many of them practiced as individuals, which is why private practice was quite common. One of the most satisfying things about medicine, if you like working with patients, is the traditional doctor-patient relationship, where one doctor gets to know you over several years if not decades. There are news articles like this which show this is changing: http://www.npr.org/blogs/health/2013/09/30/227813508/a-doctors-9-predictions-about-the-obamacare-era (Definitely See #9).
Some exceptions (I think) would be: Pathology, Radiology, Ophthalmology, Dermatology, Radiation Oncology. But primary-care oriented fields are definitely practiced in teams or are switching to that model (http://www.aafp.org/practice-management/transformation/pcmh.html) - which is sad, because it’s already hard enough to get medical students to go into primary care as it is. With more and more primary care being done by PAs and NPs, it’s not realistic to think that after years of college and med school, a med student will go for something he could have done as a PA/NP.
The concept of a physician, as an individual who knows everything, working by themselves, doing all they can for the patient, with an individual patient-physician relationship is slowly disappearing in the United States. If you’re someone whose goal is to eventually work as a solo/multi-group private practice you might want to think over your decision. A lot of doctors are starting to become employees in hospitals: http://www.hschange.com/CONTENT/1230/, which is accelerated further by Obamacare.
I think it’s fine to go into medical school with ideas of what specialties you might be interested in. You also have to be flexible. I don’t think it’s a good idea to go into medical school with the goal of, “I only want to be an ophthalmologist/dermatologist” or “I only want to be a neurosurgeon” or “I’ll only be happy if I get to do x specialty”, for 2 reasons. The first is that the purpose of medical school is to teach you about more than 1 specific specialty, since even in many of those specialties, you have to do an internship that is not in those specialties. The second, at the end of 6 years, you may not even be realistically competitive for those specialties. Currently, all those specialties are very competitive in the match. The only exception to what I just said is if you want a residency in Internal Medicine, Pediatrics, or Family Medicine. If those are your goals, then you’ll be just fine in terms of getting A residency in those fields bc there are more than enough spots available.