Stop wasting hard-earned cash on designer duds by pairing them with the wrong undergarments. Here, Jacqui Stafford, author of “The Wow Factor: Insider Style Secrets for Every Body and Every Budget,” reveals her insider secrets to suck you in, push you up and put everything in the right place.The Best… Thigh Slimmer—EverUnder the exquisite clothes of every supermodel and celebrity is… a thigh slimmer. Look for one with medium control (so that you don’t feel like a stuffed sausage), that’s high-waisted (so you avoid the muffin top look) and that extends either to mid-thigh for knee-length dresses or to the knee for ankle-length dresses. When sitting, check that it doesn’t peek out from the hem of your dress. This one by Wacoal is my go-to secret: I hand one to clients to wear under any fitted dresses or thigh-clinging skirts. It’s insanely comfortable, and it smoothes you out from your tummy to your mid-thigh. Look for laser cut edges to avoid any dreaded leg bulge.Wacoal iPant Anti-Cellulite Leg Shaper, $60The Best… Thigh Slimmer for Fuller FiguresFor all of my fuller figure darlings, try Body Wrap’s Catwalk High-Waist undergarment. The panels have varying levels of tension to help maximize the slimming effects, so you feel fully supported. It’s also incredibly comfortable and goes up to a 3X.Body Wrap Catwalk High-Waist, $48The Best… To Wear Under a Floaty DressJust in case the wind picks up and you”¨ don’t want to reveal your buttocks in a thong, cover your bases—so to speak—in a fuller cut panty instead. Find one that’s semi-sheer, seamless and has enough coverage. I’m obsessed with these boy cut style briefs from Cosabella.Cosabella Aire Lowrider Hotpants, $27.50The Best… Body Shape-Flattering BriefsFinally, someone figured out that shapewear by body shape is a brilliant idea. Enter Wacoal’s Control Freak Shapewear collection—shaping briefs designed with your body shape in mind. If you are a Circle shape, there’s a pair proportionately designed for a fuller waist and hips with panels to help lift the butt and smooth out your midsection. Shaped more like a Triangle? There’s a brief designed with a relaxed leg opening to leave room for a curvier bottom half. Genius!Wacoal Control Freak Pear Brief, $38