From PEOPLE Magazine Click to enlarge
20s

Do

KEEP HAIR CONDITIONED

Get your tresses into peak shape now, and you'll "promote hair longevity," says Beyoncé's stylist Kim Kimble. Always apply heat-protective products when blow-drying or using irons, and deep-condition monthly.

FIND YOUR PERFECT CUT

Try out different lengths and shapes "to find a style that will make you look professional and polished," says hairstylist Ted Gibson.

Don't

GO CRAZY WITH COLOR

"You want to look like a better version of yourself—not like you are still experimenting," says celebrity colorist Steven Amendola. In other words, buh-bye, pink hair; hello, subtle highlights.

WRAP YOUR HAIR IN A TOWEL

Doing so "causes breakage on the hairline," says stylist Mark Townsend; instead, gently pat hair dry.

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MATRIX

Vavoom Gold Heat Protective Dry Mist, $12; amazon.com

GARNIER FRUCTIS

Strength & Repair Melting Masque, $10.99; at drugstores

30s

Do

MAKE HAIR COLOR LAST

"Use a shampoo without sulfates, which strip color," says Kate Hudson's stylist David Babaii, and load up on conditioner. "Dry hair is weak and will result in color fading quickly."

TAKE VITAMINS

Vitamins B and E boost your immune system and can help strengthen hair "from the inside out," says Gibson.

Don't

WASH YOUR HAIR EVERY DAY

Doing so "strips the natural oils," says Gwyneth Paltrow's stylist Serge Normant. "Just rinse it and condition the ends."

FIGHT YOUR HAIR'S NATURAL TEXTURE

Who has time to spend hours in front of the mirror? Instead, "get a great cut," says Babaii, that "accentuates your assets" whether your hair is curly or straight.

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L'OREAL

EverPure sulfate-free moisture shampoo and conditioner, $6.99 each; at drugstores

GNC

Women's Ultra Nourish-Hair Formula, $10.49; gnc.com

40s

Do

FIGHT FRIZZ

Once your hair turns gray, its texture "becomes coarse," Normant says, making a frizz-control product "a must." You should also up your deep conditioning to weekly to keep strands nourished.

TRY A STRAIGHTENING TREATMENT

As you age, hair becomes more coarse—which makes this a good time to switch to keratin products, which smooth hair. You can also have your hair professionally de-kinked; Gibson, Debra Messing's stylist, recommends Brazilian Keratin treatments, which cost from $350 for five months and "give softness without damage."

Don't

GET "SOCCER MOM" HAIR

"You don't have to have the bob!" says Gibson, adding that such a style can look matronly. Instead, Normant says, "try an interpretation of the look you've always worn by adding layers or a bang for a more youthful effect."

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AVEDA

Smooth Infusion Glossing Straightener, $21; aveda.com

LIQUID KERATIN

Deep De-Frizz Conditioner, $29; drugstore.com

50s

Do

PUMP UP THE VOLUME

"The fact that hair thins out as you get older can be a major challenge," says stylist Charles Dujic, who recommends thickening products to client Sharon Stone.

BRING UP THE LENGTH

A slightly shorter cut and some layers will help disguise thinned-out hair. "If you have fine hair and you wear it one length, past the collarbone, it could look thin," says Dujic.

Don't

MISTAKENLY DRY IT OUT

With age, the body doesn't produce as much oil. That means hair products with alcohol (which saps moisture) are now a no-no, as is going outside without sunscreen on your hair.

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BUMBLE AND BUMBLE

Thickening serum, $26; bumbleandbumble.com

PANTENE

Full and Thick Shampoo and Conditioner, $6.49 each; at drugstores

HAIR ALREADY FRIED? HOW TO FIX IT

PROTECT

The first step toward hair rehabilitation is to stop breakage. Make sure you only use styling tools made of ceramic or tourmaline—not metal—which are "much gentler," Dujic says. And when combing, don't go from root to tip, Townsend says; instead, untangle hair at the bottom first, then work your way back up.

CONDITION

For hair in bad shape, apply a deep-conditioning treatment to dry hair instead of wet, Gibson advises, to allow for deeper penetration. And repeat such treatments frequently. "Do it every other day if you can," says Normant. "After a couple of weeks, you will see an improvement."

CUT IT OFF

Trims of an inch or less are enough to keep normal hair in good condition—but to overcome major damage, "suck it up and cut it!" says Gibson. The reason? As hair wears thin, "you lose the outer layer, which leaves the inner layer vulnerable to breaking down," Dujic explains. "Once you reach that point of no return, you need to cut it."