How can I teach my child not to touch others' bodies without permission?

Practice the steps as a concrete catchphrase: "ask 'is this okay?' before touching, wait for the reply, and stop if it's no." Convey on the spot that the other person pulling away, a stiff expression, or "stop" are stop signals. At home, too, showing that adults ask "can I hug you?" before touching the child's body conveys the give-and-take of consent naturally. When it doesn't go well, respond with prevention (an adult steps in, agree beforehand) rather than scolding, and praise it specifically when done.