Talk to them, they are typically more than happy to help out. Let them know of your plans early on, and if possible offer to help them in any way. It is important to have exposure to the medical profession in any way prior to going off to school. Volunteer work at hospitals is helpful. The admissions process is highly competitive.
Most students apply to roughly a dozen schools.
Public schools that are state funded have the tendency to reserve space for in-state applicants. Private schools on the other hand can have the tendency to operate under a different set of guidelines, because they don't rely upon state funds, and sometimes allow for more leniency in acceptance policy. The procedures of application start in the beginning of June and take one year. Ideally you should take the MCAT in April, and then submit your application in June, a full 15 months prior to your anticipated start date. The MCAT is a standard exam that medical schools use to rate one student against another.