Forget the trainer -- sometimes the key to looking A-list-amazing is knowing which assets to bare and which to keep under wraps. "Feel good flaunting a body part you're proud of," fashion designer and bathing suit guru Shoshanna Gruss tells Life & Style. "You will radiate confidence -- and nothing is sexier than that."

For Rihanna, that means dressing her near-flawless bod in a bikini and keeping a cover-up close by for when she wants to reveal less. "I like wearing a bikini with a cover-up that's loose, not too long and a little bit sheer," says Rihanna, 21, of a look that accentuates her legs. Of course, she still does a little prep work before a day in the sun. "If I know I'm going on vacation, I'll do Pilates for two weeks straight," Rihanna's said.

And she isn't the only celeb who perfects her bod with last-minute fixes -- and the right wardrobe choices. Kim Kardashian, 28, dishes with Life & Style on how her bottom has become so enviable. "I love to put the treadmill on maximum incline and run backward," explains Kim. "It's good to switch it up -- run forward for 10 minutes, then backward for 10 minutes. Repeat for 40 minutes total and you'll really see results in your booty." Kim says picking the right swimsuit is key. "I prefer tie bottoms," says Kim of the style that allows her to adjust the amount of coverage.

Kristin Cavallari, 22, tells Life & Style, "I have very little hips, so a string bikini gives me curves and pushes up my boobs." But she has to watch out for adding bulk to her middle. "I drink a ton of water and eat stuff that doesn't make me bloat, like fresh fruits and veggies," she says, adding that Bikram yoga (practiced in a 105-degree room) helps her sweat out excess water and get a flat stomach.

For more of the stars' quick and easy secrets to a flattering day at the beach, pick up the new issue of Life & Style, on newsstands now!