Ummm, do things you are interested in? haha, but seriously. If you like rock climbing. climb rocks, lots of them. If you like sewing. sew sweaters, lots of them. If you like running. run in races, lots of them. if you like studying. study and tutor, lots of them? lol
You don't have to be part of a club to show you're interested in other things. Also, you should join clubs that genuinely interest you and have a social component to them. For my particular case, I hated health related organizations because they were way too focused on medicine/pre-med/health/bs stuff that was interesting but just not particularly striking to me because they were way too focused. I got involved heavily in service organizations because I liked this dual mission of serving others while also having a ton of fun. The social component of these organizations gave me a chance to meet some awesome people with similar goals and have a ton of fun (parties and stuff). Leadership in these organizations actually gave me a chance to do and learn cool skills (grant writing, community outreach, blah, blah)
Don't just be in a club to say "oh, I was in this club, and I became president, and I organized meetings, and I organized talks, and recruited members, and it was soo much fun!! I want to be a doctor!!!" Be fun. One of the reasons I joined the organizations I did were because the people in them were cool and knew how to have fun. The organization's work/mission was cool too. win win.
So yeah, moral of the post is to have fun. The only things you HAVE to do for medical school are 1. take and do well in the "required classes" 2. shadow doctors 3. volunteer at places you enjoy(and at the hospital too to get that experience) 4. MCAT
everything else makes you unique and cool and interesting. If your only other interesting thing is "oh I was uh, co-founder of the, uh, american medical association at my school" then you could come off as a pretty boring person with only one focus in your life- medicine. And while that is a focus of those wanting to be doctors, don't be like everyone else. do cool and fun things. I travelled extensively; I joined fun yet meaningful organizations; I volunteered at random places outside of the hospital- just to give an example of things you could do. Do this help? I got this advice when I was a freshman in college and it was invaluable to my time as a student. So I hope this advice can help others in a similar situation as I was in at the time.
Again, have fun with whatever you do.