Common sense comes from experience, and kids need to fail as well as succeed in order to learn it. It's difficult to develop common sense when you spend a lot of time in your room where nothing much happens.

The difference between talking on your cell phone while driving and speaking with a passenger is huge. The person on the other end of the cell phone is chattering away, oblivious.

Know how to behave at a fine restaurant, which is a telltale measure of social maturity.

Learn at least two classic ballroom dances, at least one of them Latin.

Know how and how much to tip people who expect gratuities, even in the case of poor service.

Common sense comes from experience, and kids need to fail as well as succeed in order to learn it. It's difficult to develop common sense when you spend a lot of time in your room where nothing much happens.

Be able to hiccup silently, or at least without alerting neighbors to your situation. The first hiccup is an exception.