To answer your actual question, which is for advice:
High School: High grades, good test scores, ECs, leadership, volunteering, working to allow you to get into a respected school that is a good fit. It doesn't really matter which one so long as you are successful in college. Explore various interests (don't just join the premed club--my favorite club by far, and the most useful, was debate)
College: High grades, goods test scores, clinical experience, volunteering, leadership, maybe research, other ECs. Your goal is to determine if you want to be a doctor. The premed process is supposed to weed out people with other interests or who can't handle the stress. Shadow at multiple different specialties to determine which fields may interest you. You can major in anything so long as you do the premed prereqs.
You do not need to determine your specialty until med school. In general (though obviously not always), the people who go in determined on one and only one specialty find themselves disappointed as it is not as they romanticized it. The average med school student switches specialties more often than the average UG student switches majors (which I've already done twice, in just one year!). Good luck, and keep it in perspective.