(InStyle.com) -- Ever wonder how actresses like Sienna Miller look stunning 24/7? Good genes, sure. But they also get a little help from their friends

Sienna Miller and favorite hairstylist Adir Abergel: "If I worried what people thought about my look, I'd get it all wrong."

Sienna Miller and hairstylist Adir Abergel

Try to talk coifs with Sienna Miller and she'll cut you off at the pass. "I don't even own a hairbrush!" she insists. "I'm really not too attached to my hair."

No kidding. She gamely lopped off about 10 inches to play Edie Sedgwick in Factory Girl. But the actress is much less keen to part with her hairstylist Adir Abergel, for whom she has been known to cook dinner at her London home.

"Adir gets me," says Miller. "He knows I never like to look too done or polished." Her biggest challenge? "I've got quite a lot of hair, but I like it flat, so Adir squashes it down for me."

To create Miller's ideal look, Abergel flatirons her roots and combats bulkiness with FrÃ©dÃ©ric Fekkai Coiff Finishing cream. "Sienna feels most like herself when her hair is soft and airy versus set and stylized," he says.

Still, it takes effort to appear this artfully undone. It may seem like she rolls out of bed looking glamorous, but Miller says it is not that easy: "I'm very much involved in how I want to look."

Eve and makeup artist JJ Jacobucci

She dyed her hair platinum as a Philadelphia teenager, rose to fame as a hip-hop biker chick, and cavorted with a tiger -- and later Gwen Stefani -- on MTV. It seems like Eve was born edgy.

But until recently the rapper-singer-actress clung religiously to her signature look of cat eyes, dewy skin and pale pink lips, aided by the habitual application of MAC Lipglass in Malibu Barbie (she's also a company spokeswoman).

It was on the L.A. set of Eve's candy-colored video for "Tambourine" (the hit single off her fall album Here I Am) that makeup artist JJ Jacobucci motivated the star to test a new image. "JJ recently said to me, 'Thank you for letting me experiment,'" says Eve, referring to a Cyndi Lauper--inspired look that involved electric-blue eye shadow. "I have definitely opened up a lot more."

Says Jacobucci: "We were so used to seeing her in nude lips, bronze skin and comfortable colors. I push Eve to get out of that box."

The star has lately sported hot-pink lips, chartreuse highlighter on her browbones, and blue mascara with newfound confidence. "At first Eve was like, 'Oh my god,'" says Jacobucci of such intense shades. "I was like, 'Listen, trust me. I'm going to make you look gorgeous.'"

Kate Bosworth and hairstylist Renato Campora

During the last three years, hairstylist Renato Campora has seen all shades of actress Kate Bosworth.

"When I met her, she had beachy [sandy] highlights," says Campora, who brightened up Bosworth's Blue Crush--era color so she looked "more movie star, like a young Marlene Dietrich."

Campora's platinum touch sent his number straight to Bosworth's speed dial. "It's a little secret," she says of his closet coloring abilities (he's known primarily as a haircutter). "I call him months in advance!"

Naturally, she also uses him as her stylist -- it was Campora who gave her the sleek bob that solidified her status as a hair icon last year. "She was the first one to have it," he says. "And then everybody did the bob. She was the inspiration."

For someone whose biggest struggle is building volume (Bosworth has "baby angel hair," says Campora) the bob was perfect; her hair looked
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