Whether you've got itty bitty titties or mastadonic magumbos, a well-fitting bra is appreciated by many.
The bra was invented by a German engineer. So, it's not surprising that it requires Porsche-like calibration.
This tutorial by a British lingerie shop is thorough in it's instruction of the various ways to tune your top. Take note, this isn't just to make breasts look good. It's integral to supporting your structure, reducing back pain and undue stress.