A preschool child is usually not tall enough to reach a standard-sized sink. When teaching a child to wash her hands, place a small stool in front of the sink to allow the child to properly reach the faucet and a towel. Make sure she can reach the soap without having to stand on her tippy-toes or reach very far.
The best way to teach a preschool-aged child a concept is to make it fun. There are a number of ways to make hand washing fun. Provide soap in fun shapes or in bottles displaying his favorite television character. Encourage a child to sing his ABCs while washing his hands. This ensures he washes his hands for the proper length of time. Each time a child washes his hands, give him a sticker or other small reward to acknowledge his good work.
Model good behavior by allowing your preschool child to see you washing your hands often. Wash your hands with your child before each meal, before brushing your teeth or after blowing your nose. Show your child that you wash your hands after cleaning up a mess, using the restroom or changing a diaper. Tell your child why you are washing your hands to make sure she understands when she should wash her hands, too.
Make sure your child does not just run his hands under the water and say he "washed" them. Teach him to turn on the water to a warm temperature. He should wet his hands and lather with soap. Rub hands together for at least 20 seconds, making sure soap is distributed on the tops and palms of hands. He should then rinse the soap off his hands and dry them thoroughly.