Here are some pieces of information to help you get back together with your ex girlfriend:
1. Initially you should establish why you want your ex girlfriend back. Is it for the reason that you love her? Do you really want her back? Are you afraid of being alone and getting your ex back is the easiest way to stay away from this? If you don't really love your ex and you are trying to get back together for other reasons then the relationship may not be worth renewing.
2. If your chief purpose revolves around "how can I get back together with my ex girlfriend" then don't act needy or desperate when talking to her. You need to stay in control and keep your emotions in check. If you need to express your emotions or cry then do it away from her, perhaps to a friend or family member. Don't let your ex see this. This puts her up to speed and takes your power away.
3. If you can't manage your feelings or you come about as to needy this may be a turn off to your ex. Avoid self-pity and feeling sorry for yourself. Concentrate on the positive aspects of building a new relationship with your ex.
4. Keep in touch in a relaxed manner after the break up. Show her that you can keep the lines of communication open in a welcoming and casual way. Don't force the issue or press her too hard when speaking with her. Learn to be able to just say hi and keep the conversation light.
5. Something occurred to cause the end of the relationship. Make sure that you find out accurately what it was. If you want to focus on "how to get back together with my ex girlfriend" then you need to be acquainted with what caused her to run away in the first place. Once you know this you can begin working on rectifying the circumstances.