Some generic things that seem to work:
1. Do well in your classes. Aim for a 4.0 always
2. Get involved in extracurriculars. Try out as many things as you want at first until you get a feel for the one or two that you really care about and then concentrate on those. It's better to excel at one or two ECs than have 17 things going on with little to no participation. Aim for leadership roles (probably down the line, but the earlier the better).
2b. Don't let ECs bring down your GPA. GPA >> ECs
3. Volunteer at a hospital or other related health care setting (e.g. hospice). Doesn't have to be much, a few hours once every two weeks is fine. But continue doing that throughout.
4. Get involved in research if that's what you care about. You won't be curing cancer or getting first author pubs out right away, but you can learn a bit just by being there and doing the little things. Be proactive.
5. Have fun in college! You won't have this much freedom ever again.
Edit: To get into a "premier" med school, do all these typical premed things exceptionally well and do things that aren't typical. It's not easy getting into a top school. Check out the mdapps of people who have.