During college you must complete a bachelors degree in any field while completing the prerequisite courses.
Typical medical school prerequisites include:
Biology: Lecture – 4 semesters; Lab – 1 semester
General Chemistry: Lecture – 2 semesters; Lab – 1 semester
Organic Chemistry: Lecture – 2 semesters; Lab – 1 semester
Biochemistry: Lecture – 1 semester
General Physics: Lecture – 2 semesters; Lab – 1 semester
Math: Statistics – 1 semester
English: Rhetoric (Composition) and Literature – 2 semesters
Some medical schools require humanities and social/behavioral science courses.
It is also important to get good grades in college. At the medical school I attended, the average GPA is reported to be 3.85, so even one or two B's can hurt your chances of acceptance.
During college, students take the MCAT and apply to medical school.
Medical school lasts 4 years. During medical school you pick a specialty and apply to residency.
Residency for general surgery lasts 5 years.