BS MD or Pre-Med track

@Roentgen, I have looked through various BS/MD threads, and all of them recommend extensive volunteering, medical exposure, and research. How would one go about doing these things given the volunteering age requirements in most hospitals and labs? How do you even begin finding a research position if you have only taken, say, introductory high school chemistry and biology? In what year of high school is it absolutely crucial to begin volunteering and researching, and what if one can’t go around the age requirements? What would you recommend to get into BS/MD programs? What ACT/SAT score is desirable? What classes are most important (AP Chemistry, AP Biology, Physics, AP Calculus, etc., etc.) Thanks so much in advance!