Be conservative. When deciding on a new hue, make sure not to choose a shade “more than two or three shades lighter or darker” than your natural color.
Don’t go it alone. If you can, enlist a friend to help “ensure that you don’t miss a spot on the back of your head.”
Step into the light. Your bathroom’s bad lighting won’t “do you any favors” when trying to “gauge the intensity” of a new haircolor. Use natural light to see exactly what you’re dealing with and to make sure you’ve colored your hair evenly.
Take it easy. If you recolor your entire head every six weeks, “your hair will get brittle and your color patchy.” Instead, when your roots start to show, apply dye to only the regrowth. A few minutes before processing time is up, comb it through the rest of your hair.
Source: O magazine