How to Measure and Fit a Bra. not completely accurate for us big-boob girls bc alot of european companies do FF, GG and so on but it's a start for those who have no clue because the girls at Victoria secret really have no idea what they're doing.
These are GREAT hacks. And it rids the world of some AWFUL fashion faux pas. 17 Hacks Every Bra Wearer Should Know - Use a paper clip to turn a bra into a racer-back, or to hide straps that keep poking out from sleeveless tops.
An Easy Trick to Keep Your Strapless Bra From Falling Down via Tried this today and it worked. Kinda snug, had to let the strap all the way out for it to be able to go around my bra, so far it's staying up.