Rather than over-plucking your eyebrows until the skin shows through, concentrate on cutting and taming the long hairs that can make your eyebrows look like caterpillars. Using a pair of small, sharp manicure scissors is the best way to gradually thin out your eyebrows. A well-groomed pair of eyebrows will add a polished look to your face, with or without makeup.
While standing in front of a wall mirror, create the desired shape of your eyebrow with an eyebrow pencil. You can use a set of eyebrow stencils purchased at a drugstore. A set will have different eyebrow shapes; choose the one that is closest to your own. The other option is to use an eyebrow-shaping guide found in a magazine or the internet.
Pluck out stray hairs underneath the eyebrows. This will also form the under shape and arch of the eyebrow. To keep your eyebrows even, pluck a couple of hairs from one of them. Step back and take a look at your work; then move close to the mirror and pluck the other eyebrow, in the same area.
Form visible and solid starting points for the eyebrows. If you were to draw an invisible line from your nostril up, the eyebrow should start there. Where the eyebrows should end is a matter of personal preference. Keep an arch in the eyebrows by not shortening the ending shape too much.
Use your fingers to push the eyebrow hairs up toward your forehead. (Some people use a brush, but this way is easier.) Use the manicure scissors to trim off the length of the eyebrow hairs that do not fit into the eyebrow shape. This works better than plucking a long hair, which can leave bald spots in an eyebrow.
Repeat the process until all of the eyebrow hairs on one side fit the desired shape. Do the same on the opposite side. When your eyebrows need thinning, do it all over again.
Start with a professional eyebrow shaping that you can later maintain yourself. Scissors and tweezers give you maximum control when thinning eyebrows. Alternate eyebrows when thinning them out to keep them even.
Do not attempt to wax your eyebrows if they have never been trimmed before; have a professional do it. Do not thin out eyebrows when you are in a rush.