Here are several different types of organizational strategies you may wish to explore with your outline:
Standard structure: This type of organization is one you are probably very familiar with from your academic writing. It is a very versatile structure and is inherently logical in its presentation; however, if you're not careful, you may run the risk of sounding too formal and perhaps too derivative with your writing. As with all your essays, make sure you make your essay personal so your voice comes through.
In your first paragraph, you introduce the main points of your essay. In the following paragraphs, you provide evidence to support each of your main points (usually defending one point per paragraph). In your final paragraph, you reiterate your main points in the context of the evidence you presented, possibly leaving the reader with some "big idea" that takes your message one step further.
Comparison: This organizational structure attempts to draw a comparison or analogy between two seemingly unrelated things. In the case of medical school applicants, these essays usually compare a non-medical life experience/talent/interest/famous quote with the field of medicine or the applicant's desire to pursue medicine. It is common for applicants to begin with a story, personal anecdote, quote as a lead and then spend the rest of the essay describing how the lead relates to or sheds light on medicine or their goal of becoming a physician.
If you use this structure, make sure that you provide adequate reflection on how your two disparate ideas connect (or don't connect) to each other. Make your arguments explicit; don't leave it up to the audience to figure out your points. Also, don't get too abstract or philosophical in your comparisons. You don't need to say something profound; rather, just be yourself. Remember, your discussion should always lead back to you and your motivations to enter medical school.Chronology: In this type of outline, the writer takes the reader through the various steps in his/her life that led him/her to medicine. The introduction is usually the initial event that started the writer on his/her journey toward becoming a doctor. The writer then generally recounts the subsequent events in which he/she further explored and/or was further drawn into the medical profession before concluding with how all these events brought him/her to where he/she is today.