That is a really interesting questions. I don't think there is any correct answer. My high school path was very unconventional. I worked on a paint crew, worked on a fishing crew (for crabs), cut grass for my church and some neighbors, and a number of other fairly random odd jobs. I liked being outside, I liked working with my hands, and I liked being physical. My senior year going into college, I actually started my own crabbing business. All of this experience (while I never got paid well) taught me a lot and gave me some very unique experiences. I have used the entrepreneurial lessons in countless ways through college and now in my work life. I work with a lot of people who have worked in the service industry (admin, server, cook, etc) in High School and really enjoyed those.
Volunteer work. Volunteer work is great, because you are gaining experience, helping others, and it looks great on your resume! You typically get a lot more responsibility when volunteering then you do at work.