KNOW YOUR BODY

Tons of fabric or a strapless shape don't flatter petite but curvy frames like Scarlett Johansson's. "Strapless when you've got big girls is hard [to pull off] and can look slouchy," says Stacy London, host of TLC's What Not to Wear. However, Johansson's yellow Preen sheath works because "it's a much tighter silhouette that hugs her frame and is tight at the waist," she says. "And the one-shoulder works better than strapless is because it allows her to wear something supportive underneath."

Patrick McMullan/Sipa; Todd Williamson/WireImage