The first thing you need to is apologize for whatever it is that you did wrong. Don't argue with her and let her express her emotions in as much detail as she wants. Then, give her time to calm down and let the anger go and then try and romance her until she loves you again.
Just dont go crawling back to her....that would drive me nuts if someone did that to me. I would want thw guy to be a "man" and apologize without blubbering and all that. Keep it short and sweet but make sure she knows you mean it..
first thing is first be a man and apologize to her for whatever you did. tell her that you screwed up and one more thing when you are saying sorry don't laugh or turn to your friends because then she is going too assume that you really don't mean it. well i hope this helps and hope you get her back good luck