First off make sure that this is what you want to do....
Alright then,
Medical schools do not care what major you are. The only thing they look at is how your GPA is and whether you took your proper pre-reqs (and many other things). I have read/heard people applying to med school with a english major, or music major. The number one thing to remember is whatever you major in, make sure you do well in it.
Number two, as mentioned before, most medical schools require you to take these following pre-req courses.
1 Year of General Chemistry
1 Year of General Biology
1 Year of Organic Chemistry
1 Year of General Physics
1 Year of Calculus
Note: Your Chemistry, Biology, Organic Chem, and Physics are subjects that will appear on your MCAT, so your gonna have to take then anyway if you want to have a shot at a decent scores on MCATs.
Calc is required by most medical school just to see whether you are able to do work and keep at it. Generally (at least in my university) Calculus is referred as a "weed out" class.
number 3 : Generally you will have a pre-med advisor, and most of the time they are good in depicting what your next four years will be.
number 4: make sure you start your ECs, you want to have volunteer, leadership type roles, research, etc.
and finally...
Make sure this is what you want to do.