1. I've heard it said that there's one hemline that will always be correct. What is it?
The perfect hem hits the top of the knee or an inch above—no higher. Period. If you despise your knees, says O's creative director, Adam Glassman, wear a skirt or dress that grazes the bottom of the kneecap and a higher heel. But odds are your knees look fine.
2. Can I wear brown and black together? Navy and black?
There's nothing chicer. And since all three colors function as neutrals, there's not much heavy brain work involved. Especially on the upper half of the body, navy is kinder than black, which tends to draw color out of the face. "A brown or navy shoe, belt, or bag worn with a pair of black pants shows that you possess a certain amount of flair," says Glassman. To make this look no-fail, always match socks or hosiery to your shoe.
What should a woman never wear if she wants to dress her age?
3. In your 20s: Matching suits—dressing like a Park Avenue matron just makes a young person look dated.
4. In your 30s and up: Colored tights—too juvenile. Low-slung jeans, shorts, or skirts—no one wants to see muffin top or midriff.
5. In your 40s and up: The schoolgirl look—rounded collars, pleated plaid skirts, and pinafores look wrong on grown women. Short skirts—hems that hit midthigh or higher aren't appropriate no matter how hot your legs look.
6. In your 50s and up: Anything strapless—unless you're wearing a jacket or other shoulder coverage. Innerwear as outerwear—leave the bias-cut slipdress in the bedroom (and, for that matter, the terry cloth hoodie and sweatpants).
7. In your 60s and up: Bikinis—there are gorgeous one-piece swimsuits that don't reveal the whole landscape.
8. No matter your age: Nude or white hosiery—better to go barelegged with a spray tan. Shoulder pads—honestly, why? Ankle-length straight skirts—flattering to exactly no one. Retro trends—if you were old enough to wear it the first time, don't revisit it.
9. Safe at any age: Heels (two inches and up)—they make every pair of legs look toned. Jeans—there's a modern pair made for every body shape. T-shirts—a soft, fitted cotton tee always gives off an unstudied, contemporary vibe.
Arianne Cohen is a Manhattan-based writer. Her exploration of the world of tall people, The Tall Book (Bloomsbury), will be published in January 2009.
Additional reporting by Brooke Kosofsky Glassberg and Kate Sandoval.