Crop it like it’s hot: Here’s how to make the skin-baring style look sassy—not trashyHow do you make a tweed suit hip? Cap sleeves and an ever-so-slightly cropped top, as evidenced by the raw-edged two-piece Proenza Schouler number that reigning indie screen queen Greta Gerwig rocked at the Los Angeles premiere of her latest flick, Mistress America. That peek of skin gave the classic design a playful touch. And while Katharine McPhee may not have been TV viewers’ pick for American Idol, the Smash star is our idol for pairing this killer black-and-white Paule Ka ankle-length skirt and modestly midriff-baring tank at the CFDA Awards. The sleeveless extra-long Amanda Wakeley vest was an unexpectedly edgy—and smart—eveningwear choice. On Gerwig:  18k rose gold ring with onyx and 0.45 ct. t.w. diamond pavé; $7,040; Irene Neuwirth, Venice, Calif.; 310-45