As a general rule, hair should be washed as often as needed, says Amy Abramite, creative director and stylist at Maxine Salon in Chicago. For most stylists we talked to, that’s every two to three days. Any more, and you risk stripping your hair of its natural, protective oils that keep it shiny and healthy, Hills says. This is especially true for people who color their hair, as over-washing can dull the vibrancy of their color, says Constantine James, a celebrity hair and makeup expert in Chicago.

Of course, there are other factors involved. If you work out and sweat a lot, you may not be able to wait three days, Abramite says. In that case, try rinsing with water, scrubbing the scalp, and conditioning your ends only, says Paul Norton, a Joico celebrity hair stylist in Los Angeles.

To avoid greasy strands, apply conditioner on the ends of the hair, where it truly needs hydration—not the scalp, Abramite says. Start with an amount about the size of a dime (yes, a tiny dime), and try to disperse it evenly throughout the hair. If needed, up the amount, but never exceed a quarter size. “If you’re using a half-dollar size of product, you will definitely be spending a lot of money on shampoo and conditioner and not doing much for your hair,” James says.