Very young children often judge adults according to superficial appearance, and may expect that a dangerous person will "look bad" -- perhaps by having unruly hair and an unkempt appearance. Teach children that a stranger is dangerous when he attempts to lure the child away from a public setting or gain information about the child's family, and that children should judge based upon the stranger's behavior rather than his or her appearance.
Not all strangers are bad. If a child gets lost, a police officer or a firefighter could be her best friend. Teach children to gravitate toward people in uniforms if they need help by showing them what uniforms look like and giving them a chance to practice asking for help from uniformed strangers. It's also helpful for children to have a backup plan. Encourage them to seek help from people only in public locations. Parents who have children can be an ideal choice, so ask your child to look for a mom or dad who has happy, comfortable-looking children if they get lost.
One of the risks of teaching children that all people they know are good is that children might not report abuse by a relative or friend. Teach children to judge friends based upon how those treat them. Focus on helping them understand that no one has the right to touch them against their will or to harm them by hitting them. Help them understand that there are friends they can rely on if someone they know is harming them. Encourage them to turn to teachers, daycare providers and other trusted adults when they need help.
Children tend to believe that anyone who is nice to them is their friend. Teach them that when they are with an adult such as a parent or teacher, no other person has the right to take them, and they should not rely on adults who tell them that an authority figure wants them to do something. Instead, they should ask an adult they trust. Play the "bad friend" role to show a child someone who behaves in a friendly way but who, upon getting the child alone, begins behaving threateningly.