Olympia Bermann

Photo: Robert Trachtenberg

The Perfect Layered Tee
Olympia Bermann
Senior knitwear designer, J.Crew, 30

Why it's new: Sleep and workout wear no longer, these tees are soft, slouchy (in a good way), and beg to be layered. Wear two instead of a blouse or sweater for weekend errands and weekday meetings alike.

How she wears it: Bermann, who creates supersoft, flattering pieces for J.Crew, layers a striped tee and an updated take on a sweatshirt over a pencil skirt for a look that can go straight from model fittings to dinner out. "With the right accessories, I'll wear a T-shirt anywhere," Bermann says.

Why you should try it: Because it's comfortable and eclectic, yet unexpectedly chic. "I like to dress with a sense of ease," Bermann says. "Mixing casual and fancy pieces is a very modern way of dressing."

O creative director Adam Glassman's tip: Proportion is key when layering. "With a looser top, wear a snug pencil skirt, leggings, or fitted jeans."

Striped tee, J. Crew, $40; JCrew.com. Gray Tee, J. Crew, $98; JCrew.com. Skirt, Cushnie et Ochs, $795; Shopbop.com. Tassel necklace, David Yurman; 212-724-4255. Horseshoe necklace, Lulu Frost for J.Crew, $118; JCrew.com. Pendant necklace, Lulu Frost for J. Crew, $135; JCrew.com.
cream layering tee

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Layering Tee
Tee, Bella Luxx, $58; BellaLuxx.com
marigold layering t

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Layering Tee
Tee, Live!onSunset, $92; 310-360-1660
purple layering tee

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Layering Tee
Tee, Lola&Sophie, $95; LolaandSophie.com
melissa george

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The Perfect Graphic Sheath
Melissa George
Actress and entrepreneur, 35

Why it's new: The little black dress gets an update in this universally flattering sheath with ingenious white insets that carve out a slimmer silhouette.

How she wears it: George, a Golden Globe–nominated actress (for HBO's In Treatment in 2009), has a successful alternate life as an entrepreneur: In 2008 she coinvented Style Snaps by HemmingMyWay, a clever adhesive snap that instantly shortens jeans or pants; the product is now sold in 21 countries. George is similarly inventive with this sheath, pairing it with a sharp white blazer for business meetings; for evening premieres, the dress needs little more than striking heels and jewelry. "It's a power dress," George says. "But it's not boring."

Why you should try it: The geometric details make a bolder statement—and can be even more slimming—than plain black. ("If you're trying to hide parts of your body, they magically disappear," George says.)

Adam's Tip: Regardless of your age, "the most sophisticated length for a dress is either an inch below or right above the knee."

Dress, Spiegel, $79; Spiegel.com. White Blazer, BCBG Max Azria, $228; BCBG.com for stores. Necklace, ABS Allen Schwartz, $250; Bloomingdales.com. Bracelet, Danielle Stevens, $42; DanielleStevens.com. Clutch, Christian Louboutin, $1,195; ChristianLouboutin.com
black and white sheathe

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Graphic Sheath
Dress, Shape FX, $59; ShapeFX.com
striped sheath dress

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Graphic Sheath
Dress, Caché, $158; Cache.com
nue by shani sheath

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Graphic Sheath
Dress, Nue by Shani, $228; Lord and Taylor; 800-223-7440
Kelly Rowland

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The Perfect Red Jean
Kelly Rowland
Singer, actress, activist, 30

Why it's new: Just like your favorite blue jeans, red can be dressed up or down. But the color makes a crisp, vibrant statement.

How she wears it: Paired with a tuxedo jacket, silk lace top, and heels, red jeans complete what Glassman calls a "French gamine look." "I like clothes that are fabulous and travel well," says Rowland, who goes from promoting her new album, Here I Am, to events for her charity, I Heart My Girlfriends, which encourages camaraderie among young women.

Why You Should Try It: Colored denim (Rowland also owns pink and blue versions) is fun and never schlumpy. "It's amazing what one pop of color can do," she says.

Adam's Tip: Not sure you can pull off fire-engine red? "Go for a subtler bordeaux-like shade, which is easier to dress up for evening." And as with regular jeans, choose a style—whether it's skinny, bootcut, straight-leg, or boyfriend—that suits your body type.

Blazer, Paul&Joe Sister, $350; 310-270-4620. Blouse, Fifteen-Twenty, $253; MadisonLosAngeles.com. Heels, Charles by Charles David, $150; Heels.com. Jeans, Hudson Jeans, $198; Nordstrom.com. Earrings, Roberto Cavalli, $535; 212-755-7722. Cluster rings, David Yurman; 212-724-4255. Faceted cocktail ring, MNG by Mango for JCPenney, $20; 877-346-3527. Metal ring, Forever 21, $4; Forever21.com. Pin, L'Wren Scott, Barneys New York; 877-822-7639. Bracelet, Fantasy Jewelry Box, $38; FantasyJewelryBox.com. Clutch, Salvatore Ferragamo; 800-628-8916.
gloria vanderbilt red jeans

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Red Jean
Jeans, Gloria Vanderbilt, $35; Kohls.com
DKNY Jeans

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Red Jean
Jeans, DKNY, $79; Macys.com
NYDJ Jeans

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Red Jean
Jeans, NYDJ, $104; NYDJ.com
Bertha Gonzalez Nieves

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The Perfect Dressy Trenchcoat
Bertha González Nieves
Cofounder/CEO, Casa Dragones Tequila, 41

Why it's new: The classic trench gets a luxurious upgrade in buttery suede and leather. Not just for chilly workdays and Saturday brunches like its cotton and wool cousins, this coat is great for big nights out, too.

How she wears it: González Nieves, a New York City–based businesswoman who created Casa Dragones, a high-end tequila served in restaurants like New York's Le Bernardin and Beverly Hills' Spago, brings just one coat when she travels. "I prefer not to check bags, so I pack efficiently," she says. For a new take on evening wear, she pairs a trench with a sparkly minidress.

Why you should try it: Because a trench provides a refreshing counterpoint to all-out glamour at night. "I want to seem elegant yet approachable," González Nieves says. "A trench just makes an evening dress look so much cooler."

Adam's Tip: Pop the collar and push up the sleeves. "Think Catherine Deneuve in The Umbrellas of Cherbourg. That quintessential Frenchwoman with her one, perfect trench that she wears all her life."

Trench, Ralph Lauren Black Label, $5,598; RalphLauren.com. Dress, ADAM, $495; ShopAdam.com. Tights, DKNY, $15; Bloomingdale's; 800-555-74-67. Earrings, Guy and Eva. Bracelet, Noir Jewelry, $150; NoirJewlery.com. Gold ring, Trina Turk, $88; TrinaTurk.com.
leopard trench

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Dressy Trench
Coat, Victoria's Secret Catalogue, $148; VictoriasSecret.com
maroon trench

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Dressy Trench
Coat, Jane Post, $475; NeimanMarcus.com
navy trench

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Dressy Trench
Coat, Kate Spade, $725; KateSpade.com
Lisa Ellis

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The Perfect Plaid Shirt
Lisa Ellis
Entertainment executive and investor, 41

Why it's new: If you think plaid shirts are just for lumberjacks, hipsters, and your husband, think again. Fall's versions are refined and office appropriate.

How she wears it: A former music executive, Ellis helped shape Beyoncé's and Mariah Carey's careers before launching a branding company and becoming a founding partner at an investing firm. An avid equestrian, she likes pieces that can take her "to work, to the barn, and to dinner," she says. She pairs her plaid shirt with trousers, a belted cardigan, and a splashy hat. "I want to look fashionable, not like I'm wearing a business uniform."

Why you should try it: Plaid, when used correctly, is a fresh twist on office casual. "A plaid shirt with a more tailored item, like these beautiful trousers, looks put together but not overly serious," says Ellis.

Adam's Tip: When wearing menswear-inspired pieces, add feminine touches—like metallic heels—to avoid looking "too Annie Hall." And when mixing plaids, "keep colors in the same range."

Shirt, CK One, $50; Select Macy's stores; 800-622-9748. Belted sweater, NSF Clothing, $380; NSFClothing.com. Trousers, Chadwick Bell, $1,280; Bergdorf Goodman, NYC; 212-753-7000. Hat, Andean Collection, $69; TheAndeanCollection.com. Bracelets, Harriet Anthony Jewels, starting at $2,200 each; 212-334-1160. Clutch, Salvatore Ferragamo, $1,550; 800-628-8916. Shoes, 3.1 Phillip Lim, $795; 212-334-1160; Shopbop.com. Watch, Michael Kors, $180;
MichaelKors.com.
aeropostale plaid shirt

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Plaid Shirt
Shirt, Aéropostale, $23; Aeropostale.com
TNA for aritzia plaid shirt

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Plaid Shirt
Shirt, TNA for Aritzia, $60; 212-965-2188
C&C plaid shirt

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Plaid Shirt
Shirt, C&C California, $118; Bloomingdales.com
Taylor Foster

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The Perfect Lace Pencil Skirt
Taylor Foster
Bakery owner, 35

Why it's new: The pencil skirt—that timeless, slimming wardrobe staple—is not just for the office, nor should you have it only in black: This version is romantic, and more versatile than you think.

How she wears it: Foster, who sells sweet treats at tea shops and bakeries in the New York area (and online at heavenonmainstreet.com describes her style as "vintage, quirky, and classic." She pairs the skirt with a silk blouse and a cropped motorcycle jacket—a ladylike-with-an-edge look that's as appropriate for business meetings as it is for pastry tastings with her clients. Her sweet specialty? "diamonds"—nut-encrusted caramel in a vanilla cookie crust.

Why you should try it: Because pencil skirts look good on everyone—and now they're suitable for work and play. Off-hours, Foster likes to wear hers dressed down, "with flats and a tank top."

Adam's Tip: Don't get too hung up on matching—this skirt's nude underlay helps the emerald green lace function as a neutral. "It works with camel, gray, and black for day, or with something silkier and shinier for a cocktail party."

Skirt, Eva Franco, $195; EvaFranco.com. Blouse, Kolae, $225; StyleEtoile.com. Jacket, Boss Black, $495; 800-484-6267. Bib necklace, Roberta Chiarella, $58; RobertaChiarella.com. Clutch, Nancy Gonzalez, $1,300; Bergdorf Goodman, NYC; 212-753-7300.
IsaacMizrahiLive lace skirt

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Lace Pencil Skirt
Skirt, IsaacMizrahiLive! For QVC, $59; QVC.com
topshop lace skirt

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Lace Pencil Skirt
Skirt, Topshop, $80; Topshop.com
josie natori lace skirt

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Lace Skirt
Skirt, Josie Natori, $295; Natori.com