Most people may equate January with self-imposed Netflix hibernation, but let's be real: We all have events to attend. Whether it's a winter wedding, a fancy dinner, or a BFF's birthday bash, why not pull out all the stops (especially when 90% of your month is likely spent wearing turtlenecks and boots). But before you whip out all your glittery, body-con, high-slit, low-backed pieces (hey, who doesn't love dressing up every now and then?), you might want to go bra shopping, first."I advise women to go shopping for underwear before they buy clothes," Lori Kaplan of New York City's BraTenders told Refinery29. "That way, they see what's available in their size. Then, they know what they can wear on top." A good bra, as we've written about , can change everything from your posture to the way a certain article of clothing sits on you.Good bras are also pretty basic — straps that hold up your cups and a band that supports you. "Your bra should be in the same place as it is in the front, parallel to the floor,"Kaplan warns. "The underwire is snug under your armpits, the bridge of the bra flush against your sternum. There should be nothing bulging or spilling."To avoid that bulging and spilling, however, bras require some sort of strap or support. So what do you do if you want to pull off a look like Kendall Jenner's birthday dress ? How do you quell any concerns about nip slips? Ahead, Kaplan, as well as Iris Clarke of wedding boutique Iris Lingerie , are here to help us figure out exactly what to wear under all of our fancy dresses.