When beginning to comb, keep in mind that viable nits reside only ¼ of an inch or less away from the scalp on the hair shaft. This means that the comb must be flat against the scalp at the start of each stroke in order to be effective. For long hair, let out the hair of one section, comb, and clip or tie it up again.
Start with the hairline and move inward, towards the center of the back of the head. Pressing firmly (but not painfully) against the scalp, slide the comb into the hair and pull it through the full length of the hair shafts. The more hair that is passed through the comb in one stroke, the more easily the nits can be removed. If the comb is stopped by a snag in the hair, use your other hand to pull the rest of the hair’s ends through the comb piece by piece.
On the first pass, fan the teeth of the comb out over a container of water. To confirm whether the debris you’re seeing is dandruff or lice eggs, watch how it behaves. If it floats on the water, it’s nits; if it sinks, it’s dandruff. Approximately every 4 to 5 strokes, fan the teeth of the comb out over the container of water or wipe it off with a paper towel to remove the debris. Unless a louse is removed, it is not necessary to clean the comb after every pass, as lice eggs cannot re-attach themselves to the hair.
Comb each area multiple times, in horizontal, vertical, and diagonal directions, until the comb removes no debris. Comb especially thoroughly along the hairline, behind the ears, and at the base of the neck, where you will find the highest concentration of nits. Repeat until the whole scalp has been combed through. For long hair, finish by letting each section of hair out and comb multiple times over the areas where the hair was parted, in all directions.