You do it the same way everyone else does:
–complete all med school pre-reqs (bio, chem, ochem, biochem, physics, calc, stats, English, sociology, psych)
–earn a high GPA and sGPA (sGPA = bio, chem, physics and math classes only)
–score well on the MCAT
–continue your community service
–develop relationships with your college professor so that they will feel comfortable writing you strong LORs
–shadow physicians in variety of specialties so you know what the day-to-day career of a doctor entails
–engage in clinical activities where you come into contact with the sick, injured, dying, chronically ill, mentally ill, disabled and elderly so you know if you can handle spending the rest of your life ministering to them
–volunteer to do clinical or lab bench research so you can demonstrate that you understand the research process
–if possible, gain leadership roles in activities that interest you.
You can major in biology if that's an interest of yours, but it's not necessary to major in biology to go to med school. You can major in any academic subject so long as you fulfill all med school pre-reqs.
Graduate school in biology is entirely unnecessary for a med school application.