Revise your motivation. You want her back because you love, or simply because they are unable to cope with caused by pain, or just want revenge? Why did you split up? Are there any reasons why it happened will you be able to rise above them, or something has changed? If you feel that the existing problems will be solved somehow by themselves, the risk to experience another breakup. Determine why you want to review, once finished.
Apologize. It's bitter berry, but the restoration of relations requires you to dig into their conscience and be able to adequately apologize. Select a half-hour for self-evaluation and inventory of the big problems, quarrels and disputes, which led, eventually, to separation. Admit your mistake and apologize. Even if it's just a nice gesture that she will appreciate it and will consider as a step forward.
Talk. Arrange a meeting with her and tell us about their feelings and about what I would like to restore the relationship. Try to objectively admit their mistakes and show the positive aspects. Remind her of a time when you had fun together. Don't forget to highlight those characteristics that appreciate the most. But, of course, do not humiliate and do not beg. Save your dignity and manhood.