What to do with my post-bacc sciences and a word about them (med school)..

[MSK9]

^ What davewill said, plus shadowing and clinical exposure, and extracurriculars including substantive volunteering.

If a basketweaving major existed, it's realistically possible basketweaving majors would have a high med school admission rate, not because anything about basketweaving was uniquely good preparation or uniquely favored by med schools, but because the small and unusual population of basketweaving majors who then went on to qualify for and apply to med school tended to rock their science courses and MCATs.

Do what will help you rock your science courses and MCATs, and the sort of extras named above.

True story. Med schools want the applicant to have exposure to the clinical setting prior to starting. While shadowing is clinical in nature, it's not considered clinical interaction, so they also like when students volunteer at free clinics or other routes of patient care in addition to shadowing. 

While a good MCAT score doesn't guarantee a good doctor, it shows the school that the student is capable of handling the material to come.