How do I stop my child from hitting other kids?

"Scare" your child against the negative behavior. I remember how my late grandma would tell us that if we did bad things, the police would take us away. This is a stretch but technically, it is true. In the future, if the negative action continues when he is older, he can get into trouble with the authorities. Also, you can try reverse psychology. Ask him how he would feel if someone were to hit him. He shouldn't do on to others what he does not want done to him.