Undercover Agent: All the Bra Mistakes You're Probably Making—and How to Fix Them

The celebs' secret to getting dressed—and always looking camera ready—is all about the part of an outfit we seldom see: the bra. These girls know better than to be caught with lumpy lace under a whisper-thin tee or to wear a cut that creates unmerciful backfat.
Why? Because despite what men's mags or lingerie commercials tell us, wearing the right underthing isn't about being sexy or showing off lacy bits. When it comes to fashion, it's about creating the right silhouette so our clothes (from T-shirts to ball gowns) hang beautifully. With the right bra, we carry ourselves with better posture, can appear more slim and more put-together—even when straps are purposefully peeking out.

No matter what your fashion M.O., this is one element of celebrity style we should all adopt. Below lies the secret to going from trashy to classy in an instant, all thanks to an often-overlooked underpinning.
Relearn your A, B, Cs: Most of us know that band size is measured by the circumference of the rib cage. And cup designation account for the size of the twins. But many don't think about how each are related—and that's how many of us end up wearing bras that don't fit.

The bigger the band size, the wider the "U"-shaped cup. So if your band size goes up, from a 34 to a 36, but the size of the girls actually stays the same (say, a "B") you may need to reach for a 36A to retain the right fit. Conversely, if you go down a band size, you may need to wear a larger cup size to keep ‘em covered and prevent the bra from cutting into your side boob.

Dave M. Benett/VF14/WireImage

Hook yourself up: We love the look of a dainty bralette equipped with a single-hook closure. But these narrow bands aren't always enough to support the twins (hello, saggage in the front and skin bulge on the back). Ditch the rolls by going with a bra that creates seamless lines with your skin; oftentimes, the wider the bra band and more plentiful the hooks, the better the support in front and smoother the silhouette in back.

Account for sag: Wear and tear can cause a bra band to stretch up to two inches, depending on its fabric and how you care for it, wrote Rebecca Apsan in The Lingerie Handbook. The owner of renowned lingerie shop La Petite Coquette suggested that we buy bras that fit on the loosest hook settings so we can keep a snug fit when compensating for stretch down the road.
n Hollywood: Taylor Swift, Emma Stone, Kristen Bell. Have you ever seen them picking up fallen bra straps when out and about? No way. Because these stars know that the fastest way to a disheveled look is to allow bra straps to dangle alongside your arms. Make it a habit to adjust your straps every time you put a bra on. That's right, Every. Singe. Day. Since strap settings tweak with wear and in the wash, frequent re-calibration is the only way to ensure they stay on your shoulders. Even out with padding: Let's face it: Most of us don't have perfectly symmetrical features—and it's totally normal to have one breast that's a bit smaller than the other. Create the illusion of a balanced set by using padded bras to your advantage. Pick a bra with removable padding and use it in one cup only to cushion the smaller side.