5) You are never in any case to date a friends ex or a guy who she was really into.
Exception: If he's one of those guys who every girl likes.
If a guy your friend is into asks for your number, you are to deny it and walk away, and/or slip him your friends number while saying, "I think she is more your type, you should call her".
Chicks before Dicks. Simple.
When a friend is drunk, never allow her to dial, drive or leave with a random guy.
Don't be a hater. If a girl walks in looking gorgeous, girls automatically try to find something bad about her. But who knows? She could have just lose a friend, or got dumped, etc. So be nice and stop hating.