1) Go to the websites of the various hospitals in your area. Many have pages dedicated to volunteer opportunities, high school student internships, etc.
2) Regularly view the employment opportunities page for the hospitals in your area. Although you may not get a clinically relevant position, getting a position in the hospital can open doors to other opportunities in the future.
3) Talk to any physicians you know about shadowing them or if they'd provide information on other physicians you can shadow.
4) Google search for opportunities at various medical schools. This can often involve an application process and be time-consuming, but if you're truly interested in medicine, you'll have a lot of time-consuming application processes in the future. 😉
Good luck!