5 tricks to master at-home hair color

Stop staring at that drugstore wall of boxes like a zombie! Here's how to know what you need:1. If you're more than 25 percent gray or want to lighten your color, buy a permanent formula, says Avon colorist Lorri Goddard, who counts Reese Witherspoon as a client. Try Garnier Nutrisse Nourishing Color Cream, $7.99, or a foam formula, which is a bit easier to maneuver, like John Frieda Precision Foam Colour, $12.99.2. To deepen your existing tone or even out highlights, get a kit that's demi-permanent. We like L'Oréal Paris Healthy Look Crème Gloss Hair Color, $9.99, which fades within 28 washes.3. "For the best results, stay within two shades of your natural tone," says Clairol colorist Marie Robinson, who works with Michelle Williams. Ignore the picture on the front of the box--it doesn't take your starting point into consideration. Instead, look at the "before" and "after" photos on the side panel for realistic results.

A smudge on your forehead is a telltale sign of a self-service dye job. To prevent staining, apply your regular facial moisturizer along your hairline, then tap petroleum jelly there and on the tops of your ears and the nape of your neck. "Doubling up protection will stop pigment from seeping into skin," Goddard says. If you still end up with a splotch, rub it with a cotton ball dipped in baby oil or lemon juice to loosen the dye.

"The fine hairs around your face absorb color quicker, so it's best to give more processing time to the back of the head," says colorist Denis De Souza of the Andy LeCompte Salon in Los Angeles. Try what Goddard calls "the drop-down technique": Part your hair into two horizontal sections from ear to ear; secure the top section with clips. Starting with the bottom half, work in two-inch chunks to smooth the dye from scalp to ends. Then, pull down two-inch pieces from the top, repeating until you've covered your entire head.

To touch up your roots only, use this foolproof technique from De Souza: Apply conditioner all over dry hair except for your roots, then paint just the regrowth with dye. "The conditioner acts as a barrier, so the new shade blends in seamlessly," he says. (Try Clairol Nice 'n Easy Root Touch-Up, $7.99.) In a pinch, hair mascara like No Gray Quick Fix (pictured), $5.99, does the trick until your next shampoo.

If you hate the shade you chose, one treatment with Color Oops, $12.99, removes hair dye completely. Or, if you just need to tone it down a notch, try this homemade recipe that Goddard swears by: Mix ½ cup baby shampoo with 1 Tbsp baking soda and work it through your wet hair. Cover your head with a plastic shower cap and blast it with your blow-dryer for three minutes. Then rinse and follow with shampoo and conditioner. Looking at a major mishap? All three colorists agree you should let a pro fix it.