In order to get back with your ex you're going to need to think outside the box. When most people are trying to get back with their ex they almost always do the wrong things.
That is why listening to your friends might be the worst thing you can do because chances are they'll tell you to do the exact opposite of what you should really be doing.
Here is a list of some Do's and Don'ts. Follow this list and you will have a much better chance of getting back with your ex.
1) Harass, badger, nag, or threaten. No one likes to be pushed. Don't chase after her. She already gets the fact that you still care and you want her back, now it's time to back off a little bit and give her some space.
2) Lock yourself in your house and never go out. This is what many people do. They go to work but other than that they just hide in a dark room.
3) Hookup with someone else. Not only is this a good way to lose your girlfriend for good, it's also unfair to the new woman. You would just be using her to get over your hurt.
1) Give your woman some space. Give her time to miss you. She can't remember you fondly and miss you if you are constantly in her face. This can be very difficult to do but it's one of the most important things to remember if you want her back.
2) Go out with your friends. Try to have fun. It will be hard, but it's very important not only for your mental health but also so that your ex will start to see you, again, as a fun loving person. The way she saw you when you first got together.
3) Be honest about whether or not the relationship is worth saving. Not all relationships should be saved. Also be willing to honestly admit whatever part you had in the relationship falling apart and be willing to make some changes to your behavior.
Follow the steps I've listed above and you'll be much more likely to get your woman back.