Rule 16: The proper number of stairs.
Flights of stairs usually contain between 8 and 16 steps - and the number does matter, incidentally. From best to worst:
9,11,13. They're all bad.
Two quick stories: The Comfort Suite in Green Bay is a pretty nice place to stay - except for their staircases. One staircase has two flights, each with 8 steps. Nice . EVERYWHERE ELSE it is 7 and 9! WHAT??!? JEEZ.
Working at the Wisconsin Historical Society Headquarters building is both good and bad - one of the best things about it is that the flights of stairs are all 16. It's gorgeous.