Photo: Peter Rosa

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Myth: You should always shampoo before conditioning.

Fact: If you're like most people, you've always shampooed first. But there are advantages to reversing the age-old routine, especially if you have fine hair. To add softness and shine, conditioners leave behind oils, silicones, or polymers, which can be too heavy for fine strands. But if you apply conditioner first and leave it in your hair for five to ten minutes, the conditioning agents penetrate the strands and coat the cuticle, protecting hair from any harsh cleansers in your shampoo, says Wilson. Then, as you rinse post-shampoo, residual conditioner is washed away, helping to keep hair from falling flat.

Myth: If your hair tends to look oily, you should cut back on shampooing.

Fact: Washing less frequently has no effect on the amount of oil produced by the scalp's sebaceous glands; that's a matter of genetics and hormones, says Fusco. In fact, by allowing oil and dead skin cells to accumulate, you could develop a scalp condition, like dandruff.

Myth: You should avoid any product formulated with silicones.

Fact: Silicones add a thin coating to hair, which keeps out frizz-inducing moisture and smooths the cuticle so styling products and treatments can be distributed evenly and hair can be combed easily. But not all silicones are created equal: Heavier ones, like phenyl trimethicone and dimethicone, can make fine hair limp and lifeless, says Wilson; instead, use a product formulated with amodimethicone or cyclomethicone, both of which can leave hair silky without weighing it down.

Color Commentary: If you're the fine-haired type, you may be a daily shampooer—but hold off on the day you plan to dye. Hair that's squeaky-clean (or too dirty) may color unevenly, so it's best to shampoo the night before, says Hill. Bonus: Next day, the sebum on the scalp and hair shaft may help prevent irritation.

Dress, A.L.C. Top left: Necklace, Sarah Magid. Center: Necklaces (from top), Aurate New York and Bonheur Jewelry.