Signs of a Bad Fit

This is an article I've written, rewritten and revised a thousand times, and I still scrap it in the end. Look: the bottom line is that there are a million different articles out there about bad fit, some way better than anything I could write. Do the research. I'll just give you a few starting tips here to help you out.

1. The band is supposed to be tight. I can't stress this enough. A band that actually fits you properly is most likely going to be a lot tighter than what you actually wear. If you're going to wear an underwire that doesn't actually fit right you might as well go bralette; you're just not getting support. If the size up does not feel tight but the "correct" size feels a little snug, give it time. They break in and loosen up. Even the loose ones do, which makes them looser and in turn makes them fit you even more badly.
2. There shouldn't be a ton of space between your bra and your armpit. If there is, you are wearing too small a cup size.
3. If you aren't filling out a full cup, but going down a size results in quadro-boob you may be bottom heavy in the breast and need a demi-cup. That's okay. Try on lots of brands and lots of styles because no one style fits all, and what looks great on those models will not look great on you--even if you are a size 0 and have a six pack. 
4. Wrinkling in the cup is a sign that there is a little too much space.
5. If the band rides up in the back, it's too big. When a band is riding up in the back (yes, even by a little bit) it means the straps are compensating because the band itself isn't staying put horizontal to the floor. Try going down a band size.