I recommend you follow these steps:
1)Go to a 4-yr school
2)Meet the pre-health professions advisors (most 4 yr schools have them)
3)Follow all of their advice.
The advisors will probably tell you to take 2 science classes a semester (to fulfill your basic science requirements: a year of biology, chemistry, physics, and math). While you are doing this, you need to join the pre-med club on campus (support group) and get some kind of leadership experience, do volunteer work at the hospital, shadow doctors, possibly do some undergraduate research or get your EMT license. Make sure that your extracurriculars don't get in the way of your grades though: some might say otherwise, but a high GPA and MCAT score are the most important thing to get out of your undergrad.
This is the basic formula to get into medical school, but don't take it from me, make sure to meet with your pre-health advisors!