Ask yourself if you were meeting her needs by listening to her and responding to what she wanted, such as going to places that she wanted to go, like to a museum instead of your favorite bar. Don't beg, stalk her or act desperate---that's a repellent to women.
Cut yourself off. When a woman breaks up with you, she just wants or needs time alone. The time alone may cause her to miss your face and the sound of your voice if she doesn't hear from you at all and she may feel regret. Do this for at least a month.
Make yourself irresistible, doing good deeds, being the guy she wanted you to be and you wanted to become. Women find confident and successful men irresistible. You want her to suddenly think that she's losing out on the man she always wanted.
It helps if you have similar friends and you are being proactive on moving forward with your career and doing some positive things in your life such as volunteering for Habitat for Humanity. These kinds of positive messages will get back to her through mutual friends that may cause her to miss you more and she may contact you first.
Take it slow. Women can't stand men who hover, have a self-confidence problem and don't know how to talk to them. Ask her questions about subjects that are important to her, such as her career and what she sees her life being like in the future. Take her out for coffee. Listen.
Fight for the relationship once you get back into her good graces. Many men become complacent once they are in a relationship. A woman wants to know that her man is happy to be in the relationship and is very passionate about her. Women tend to watch romantic movies, read romantic novels and are fed the whole white knight thing while they are growing up. FYI, the white knight is passionate about his woman, he is self-confident enough to still stay somewhat aloof while demonstrating that he would give his life for her. In reality, a woman doesn't want her man to jump off the building because she broke up with him, but if he acts like a dead fish during the relationship, she is secretly hoping he will show his passionate side for her and do something outrageous to show her how much he loves her. Perform a romantic gesture like a horse carriage ride or a ride in a helicopter.