[See: How Safe Are Your Cosmetics?]
Don't: Overdo the appliances. Even if they're pricier, invest in good tools. Make sure they offer different heat settings and, in the case of flat irons, display the temperature. Hair dryers should have a diffuser to help distribute heat more evenly. Still, it's best to let your hair dry naturally whenever possible. Blow-drying it can cause roughness, dryness, and loss of color, according to a 2011 study published in the Annals of Dermatology. Reserve dryers for special occasions, and keep the air cool. Beware flat irons, too: While they may make your hair look smooth and sleek, they can also turn it dry and brittle, leading to frizz and heavy-duty breakage. If you must use a flat iron, keep it on the coolest heat setting possible. And don't even consider turning it on until your hair is completely dry; otherwise, you'll end up with a lot of steam and damaged locks.
Do: Brush the right way. Spend some time brushing each morning to remove dust, dirt, and dry scalp material. But if you're untangling wet hair, use a wide-tooth comb, since a hairbrush will be too harsh. Opt for a brush with a natural bristle instead of one that's metal or plastic, Hammadi says. They're less likely to needlessly pull hair out.
Don't: Overwash it. Shampooing and conditioning every other day will suffice, unless your tresses are extra oily. Washing too frequently causes dryness, Hammadi says. "If you constantly overwash, it's going to become too clean," he says. "Just like when you wash your clothes too much—they fade. It pulls out too many of your natural oils, so you won't have as much shine." This is particularly a concern if you've colored your hair; red and blonde tones are especially likely to fade if you shampoo too often. Note, however, that you don't need to wash with cold water: That's just a myth. Warm water works just fine.
Do: Maintain it with regular trims. Parting ways with even half an inch can be excruciating if you're in pursuit of long, luscious locks. But it's necessary. Ideally, head to the salon every six to eight weeks, though you may be able to push it to 10 if you're trying to maintain length. Regular trims keep split ends from splitting more and more (and looking worse). Those with an intense styling routine—straightening or curling every day—typically need more frequent trims than those who sport a more natural look. One way to tell if it's time to call the salon: Inspect the bottom of your hair. If it doesn't come to a blunt end, you may be overdue.