[Serious] What did your parents teach you about dealing with strangers? How did they teach you it?

Growing up I was simply taught not to be an idiot and to stay away from people I didn't know. Considering that I, at the time, lived in the middle of nowhere I didn't get out much so that wasn't a big deal to me.

But for kids who grew up around people, what did your parents teach you? I have a friend who staged having his daughter kidnapped so that she would never talk to strangers again, and... well I think that's going really overboard and is a great way to traumatize someone for life. But honestly, I'm no parent and don't really know enough to criticize his parenting, you know?

So, reddit, how were you taught to handle strangers?