All Dressed Up

Dress Code: "Casual"
Harriette Mandeville, 61; actress and leader of meditation workshops
"Wearing one piece means I don't have to figure out what goes with what," Harriette (left) says. This low-priced stretch charmeuse number (Isaac Mizrahi for Target) makes life simple. For informal evenings, ground it with black: a swingy jacket (H&M), wristlet (Dior by John Galliano), and shoes (Rodo). Anthony Nak earrings.

Dress Code: "Festive"
Hitha Prabhakar, 31; fashion editor and stylist
"People let go at end-of-the-year parties," Hitha (center) says. "They're more unguarded." To match that happy mood, we punched up the fuchsia strapless (a built-in bra means you don't need special lingerie) with high-intensity accessories: an embellished necklace worn as a belt (Beavaldes), glam earrings (Kenneth Jay Lane), and metallic shoes (Rodo) that can dance all night.

Dress Code: "Black-Tie Optional"
Marina Aris, 33; financial adviser
"Dresses make me feel va-voom!" Marina (right) says. This time, our sheath goes formal with diamond jewelry (Tiffany & Co. studs; Fauxsie by Baby Doll Gems choker; Asprey bracelet) and a filmy wrap that's just a length of tulle (B & J Fabrics). Stuart Weitzman shoes.