1 - Only wear your hair up one day a week.
2 - Only wear jeans on track-pants on Friday.
3 - On Wednesdays they wear pink.
4 - Ex-boyfriends are off limits to friends.
And I'm not completely sure about the fifth, sorry!
I don't think they are ever mentioned in the movie. I know that the words "unwritten social rules" are in the synopsis of the movie, but i don't think they were ever verbally said or written down.