To help you do the same, we turned to two of those gurus -- Nicole Chavez, whose clients include Catherine Zeta-Jones and Scarlett Johansson; and Phillip Bloch, stylist to such stars as Sandra Bullock and Halle Berry, and author of "The Shopping Diet: Spend Less and Get More." Use their insider advice to master your top dress-slim challenges.
One word: shapewear. "It smooths and reshapes, but also helps you stand taller," Bloch says. "Shapewear makes you more conscious of your posture."
Invest in a high-waisted shaping bike short, Chavez advises: "It's one-stop shopping -- for the stomach, hips, thighs." It's also important, she adds, to not buy clothes that are too fitted in that area: "Go up a size, then have them tailored to your dimensions so they fit you perfectly."
And what should you wear on top of your slimming underthings? An empire-waist dress is flattering, as are A-line dresses, because "they graze the stomach," Bloch says. "You can also put a wider belt -- 3 to 4 inches -- over the tummy, especially in a darker color. No skinny belts. You're looking for a corset-like belt."
What's the most surprising figure complaint you hear from your celeb clients?
"Every woman I dress complains about the skin under her arms," Bloch says. "No matter how thin they are, the triceps area bothers them."
To cover it, he suggests illusion T-shirts -- a sheer top over a tank top, "sort of like what Helen Mirren wore at the Oscars." Also, he adds, "a little shrug or cardigan will cover that area. For fuller arms, go for a full cap sleeve."
Do you have a foolproof outfit for a star who has gained a few pounds?
"Star or no star, a great-fitting black dress is a great go-to," Chavez says. "The classic is short-sleeve or 3/4-length sleeve, fitted at the waist, slightly above the knees."
Above all, "when you feel you've added extra pounds, don't go baggy. That's what we all feel like doing, and it's the worst thing you can do," she says. "It will just make you look heavier. Instead, wear something tailored."
Which colors besides black are slimming?
"Purple, navy, burgundy, the jewel tones -- anything in those rich hues," Bloch says. "Eggplant, charcoal gray, deep emerald. They all do the same thing. Also, what I call petroleum colors in blue, gray, green."
But black can't be beat, say the experts, and you can always make your LBD feel more fun with bright accessories. "Add a red shoe or a green handbag," Chavez suggests.
Can the right accessories really make a difference?
"A larger necklace can make you appear taller and leaner," Bloch says, because it directs attention up and away from your figure flaws. Depending on your body, a choker can be good, drawing attention to the neck. But if you have a big bust, choose a necklace on a short chain instead.
Accessories like earrings or sparkly headbands are great distractions, he adds, drawing attention "to where you want people to look. Remember Fran Drescher's great quote: 'The bigger the hair, the smaller the hips will look.'"
What's the best way to minimize a big bust?
"Bra-fitting is crucial," Bloch says -- and it's available for free at most department stores. If you're chesty, look for a bra that both supports and sleeks you.
When it comes to the clothes you put over that bra, Bloch says, "You need to leave the neckline open -- create a V, an upside-down triangle, so you pull the eye down toward a narrower place. A vest over a shirt is nice. If you wear just a shirt or blouse, open the buttons and wear a tank top underneath. Overall, it helps to create a sleek, column-like effect," Bloch says. "Christina Hendricks, Halle Berry, Salma Hayek -- all the curvy girls create the illusion of length."
Dressing Hendricks for the Screen Actor's Guild awards, Bloch chose a Carolina Herrera gown with a big red bow on the shoulder: "It created a long, sleek silhouette that drew attention upward," he says. "It was elongating, not eliminating."
So, what styles make you look tall and thin?
"Head-to-toe in one color creates a long, thin line," Chavez says. "You can even wear all white or all tan. And you'll always look taller wearing a heel or a wedge rather than flats. Even a kitten heel will make you look taller."
Bloch suggests choosing shoes in a color close to your skin tone, to lengthen the legs: "No ankle straps, which will cut you off. And those shoe boots are terrible -- not with skirts, please. They cut off the leg."
Slimming jeans are hard to find! Which styles will pare me down?
"Look for a slim fit or flat front," Chavez says. Bloch's advice? Avoid both very high- and low-waisted styles and go for a more-flattering midrise jean. Finally, when hunting for the ultimate skinny jeans, keep in mind Bloch's golden rule: "the darker the better."