11 times you should always say no to your kid

This one tests a child's inner radar. "If someone is being mean to another kid — even if the person who's being mean is a good friend of yours and the other kid is someone you don't really know or even like — you do not join in making someone feel bad," Markham instructs parents to tell their kids.

In our society, being nude in public is not OK after a certain age, says Markham, who says four years old is the limit. "Bodies are wonderful — they're strong, beautiful and special — but some parts are private and you don't share them with everybody," she says.

Airlines have certain rules and regulations that must be followed, regardless of age. Kids "can't kick the seat in from of them, can't put the tray table up and down, up and down which could easily bother the person in the seat next to him, can't be loud on the airplane," Markham says. "It's a communal space."

Being confined to an airplane seat for a long time takes its toll on anyone, so Markham does recommend walking around the cabin with your "in-flight entertainment."

The stranger thing is a bit tricky, says Markham, since we're always talking to strangers as adults and kids need to know there are safe strangers. "Most adults are trustworthy," she says. What's more applicable here is if a child is alone without a trusted adult.

Children need to be told that they should "never under any circumstances go with someone they don't know" or with any adult the parent hasn't given them express permission to be with.

A rule in Markham's family was that you couldn't break an agreement you made to spend time with someone just because you got a better offer. "It's consideration for the other person," she says.

For example, Markham says, say you made plans with a friend after school, and another friend says, "Come with us, we're going to get ice cream," and that's what you really want to do. In that case, you can't tell the first friend that you're not going to get together with them. "You can ask if your friend can come, too, but you're not going to break the date with the first kid," Markham says.