Where wigs are purchased you can also buy products designed specifically for taking care of your wig or hairpiece. These products are somewhat expensive but are made especially for shampooing wigs. If the wig is a human-hair wig you can use most any good shampoo which states that it is for permed, colored, or processed hair.
Use a wide tooth comb or a pick to first remove all the tangles from the wig. Turn the wig inside out before beginning to shampoo. Mix shampoo that's meant for synthetic wigs with the appropriate amount of cool water, according to the shampoo manufacturer's instructions. If using regular shampoo for a human-hair wig simply mix a teaspoon of shampoo with cool water.
Gently pour about half of the water through the wig cap before turning right side out and using the rest. Work the shampoo throughout the wig and hair gently but don't rub the cap as you would your scalp. When finished shampooing use cool, clear water to rinse suds from wig and cap. Do not twist or wring the wig but hold the hair between thumb and fingers, sliding downward to remove water. Don't pull while doing this but gently glide your hand down the hair.