Talk about the power of touch. Begin with a simple conversation with the preschooler in which you talk about reasons why people touch. On a sheet of poster board, make a list of ways in which people touch, both positive and negative, such as hitting, hugging and holding hands. Have the preschooler draw pictures of touching in these ways as you talk about which ones are nice ways to touch and which are not.
Read about nice touch. Read your preschooler a book about the topic, such as "Hands Are Not For Hitting," by Martine Agassi, Ph.D. This book shows your preschooler how nice touching should look, and outlines why it is important to touch nicely.
Practice nice touching. Ask your preschooler to show you what a nice touch looks like by having him give you a hug, pat you on the back, or hold your hand. Reciprocate, to show him how happy a nice touch can make you feel.
Reward nice touch. Monitor the preschooler's behavior and, when you see him touching in a nice fashion, reward him for doing so, giving him small prizes each time you notice him engaging in nice touch.