The hope is that people who are drawn to a life of service through medicine will by their natures seek out opportunties to serve the community as a volunteer. So you should do something that interests you and nurtures your desire to be of service to others.
The expectation is that people who think that a career in medicine might be a good choice for them will take some time to find out what the career entails including the work environment(s), the hours, duties, roles of other members of the team, "the typical day". Many applicants to medical school get this background by shadowing physicians, others have worked closely with physicians or have members of the immediate family who are physicians. The question comes down to "how have you tested your interest in medicine as a career?"