Something that my mother always swore by was teaching the child that pulling hair hurts. The only way to do that was if we pulled her hair, she would pull ours a little bit. If we stopped pulling then she would stop. If we pulled harder, then she would pull harder. It worked with us and I have seen it work with other children as well. Some might think it is cruel, but how else do you teach the child that it hurts when you do that to someone else? It only takes one or two times and the child understands not to do that, because they don't like the consequences of their actions.