Of course before you even start attempting to get your girlfriend back, there are some things that you are going to have to do. First of all, you're going to have to take control of your emotions. While the dissolving relationship may have left you feeling heartbroken, you can't appear depressed and sad if you want to go out there and get your girlfriend back. So, it's time to work on yourself a bit.
Don't be in a rush to start making moves aimed at getting her back. Slow down and get yourself into a cheerful but determined state of mind. Clear thinking now is essential so that you can formulate an effective plan for reunion.
You must at least appear to feel strong and confident even if that isn't really how you feel at all. Above all, do not appear desperate. Weakness is not a trait that women admire. Don't phone her or try to contact her in ant way. Don't "accidentally" bump into her on the street. If you do these things you will make your problem worse.
Be very careful what you say to others as well. Assume that anything you say will eventually get to the ear of your ex. It's best not to say anything, good or bad about your ex right now.
Be sure that you look after yourself physically as well as mentally. You need to look your very best right now. Start working out, buy some new clothes or get new and different haircut. Your ex girlfriend will eventually see you and you want her to take a second and maybe a third look at you.
After you are sure you are confident enough to handle talking to your girlfriend, a quick phone call may be a great idea. However, you want to make the phone call brief and to the point. Let her know you wanted to check up on her, and then do something that will spike her curiosity. Consider telling her you want to just talk to her sometime about how she really helped you out with the breakup or use some other line to get her curious enough to talk to you.
It's best to have a plan A and a plan B because you will never know for sure before hand what will work out for you. The important things are to go slowly, don't rush her and to maintain your own confidence and good humor.