Between uses. To remove color (particularly important on brushes used to apply more than one shade, such as those meant for eyeshadow or lipstick), hold a damp facecloth or facial towelette in the palm of one hand and your brush in the other. Slowly swirl the bristles of the brush across the damp cloth until they are clear of makeup. Lay the brush on a clean paper towel to dry.
Twice a month. Remove bacteria, oil and excess product with a spray-on makeup brush cleaner like Sephora's Daily Spray Makeup Brush Cleanser ($6 for 2 oz; ). Apply several pumps of solution to the brush head and use a tissue to wipe off from the base of the bristles to the tips.
Four times a year. For a deeper cleaning, wet the bristles of the brush with warm water. Add a drop of a gentle cleanser (your everyday face wash will do) to the brush head and gently rub the bristles between your fingers to work up a lather. Rinse and squeeze out water from the base of the bristles toward the tips to help reshape. Place on a flat surface to air-dry.