DEAR MISS MANNERS: If you know someone is home and have an appointment with them, but they don't answer after the first knock or doorbell ring, do you knock again? How long do you wait before you knock or ring the doorbell again?
GENTLE READER: You are allowed three rings separated by two knocks, all far enough apart to allow someone to -- well, to wash up, not to put too fine a point on it. No throwing pebbles at the windows. Miss Manners suggests using the waiting time to get out your organizer to check the date and find a telephone number with which to rouse your host.