You must condition when you're done. "If you skip the conditioner step, it leaves the cuticle open and the color keeps working," says Ionato. "So don't be surprised if you end up with much darker hair than you wanted." Don't throw away the conditioner in the kit, and if you do, make sure to use a deep conditioner in the shower after you rinse out the dye.
Section, section, section. To avoid patchiness, create a middle part that runs to the back of your head and split the hair into four sections two in front of the ears and two in back. "Always apply the dye from back to front," says colorist Aura Friedman, of the Sally Hershberger Downtown salon in New York City. "That way the dye is sitting on the back of your hair the longest, which is naturally darker than the front anyway."