How to get your ex girlfriend back depends heavily on your situation. Did she leave you? Did you leave her? What was the reasoning for the breakup? Why was it that the romance ended? How did it come to be that this relationship ended?
If she left you the the way how to get ex girlfriend back is to find out what it was about you that caused her to breakup with you. Did you treat her poorly in any way? Then it could be that you don't deserve her, unless you make some serious changes. Don't let the changes be superficial. Look closely at yourself and use this as a moment to really step back and see how you can improve the way you treat others.
What were the complaints that she had of you when she left you? Take a close look at those criticisms and ask others if there is any truth to what she said. How can you figure out how to get ex girlfriend back if you aren't willing to change what drove her away in the first place.
Did you leave her? If you made a mistake and let her go and now are trying to figure out how to get ex girlfriend back, then you just need to see how badly you hurt her. Find out if she is holding any resentment towards you because of what you did. It could be that she needs a little time away. If that is the case then let her have it. Don't be too far away but don't smother either.
You are going to have to convince her that you know you made a huge mistake and that you aren't going to do that again. The best way to do that is to give her the space and time to see for herself that you aren't just going to run off to the next one. She has to see that you are willing to stick it out. You made a mistake, you have to deal with the consequences which may mean you waiting for a long period of time. If she is really worth it then you will do it.
If the reason that the you and your girlfriend broke up is because the relationship just dissolved then, when you talk to her, let her know that you really want to get back together but you want to work hard to make it happen. You will have to convince her that what you two had was really special and that you are willing to go and get relationship advice to make it work. If she feels that you really believe that it is worth working on and that you are willing to get help to make it work then she may need no more convincing.
The real way how to get ex girlfriend back is to just take a good, honest look at what happened to bring the love to an end. Look at the mistakes that the both of you made, especially yours, and do something about it. You can't do anything to change her but you can change yourself and when she sees that you are willing to do it you may have found how to get ex girlfriend back.
To find out more read The Magic Of Making Up