In my opinion, the best way to figure out what size breast implant you would like is to do the rice test. The rice test involves getting small ziploc bags and filling each bag up with about 100cc of rice which is roughly 3oz. After you fill a bunch of bags up put on a non padded bra and put a fitted tank top on. After you have the bra and tank top on, fill each bra cup with a few bags of rice at a time. Check yourself in the mirror after each ziploc bag placement. This will give you a rough idea of what size you may be comfortable with. Also I usually suggest walking around in public with the bags in place to see how comfortable you feel with a larger bust size.
Dev Wali, MD Board Certified Plastic Surgeon