You can't approach women because you're afraid to fail.
You're afraid that some girl will reject you, which will completely shatter your mental state whilst also humiliating you in front of your friends.
That being said, the most fruitful thing you can do is BECOME a fun, sociable, likeable guy that exudes confidence and naturally attracts women with his genuine behavior.
Once you become that guy, you've found the so-called best way to get women.
The best way (and yes there's a best way here) to get your ex back is to completely change your entire self-image, whilst staying in touch with her so that she can see the changes.
Think of it this way: she broke up with you because there was something wrong that you did.
You will only be able to get this girl when you manage to see her as any other girl out there.
This is a pointless question, but it still gets asked a lot. What may work for me will never work for you, and vice versa.
Until you learn to ACCEPT and EMBRACE rejection as part of LIFE and as something that NEEDS to happen in order to get laid, you will always be unable to approach women.
Not me or any other man/player/God out there will ever be able to tell you how to get that one girl.
Ninety-nine percent of the time, you will get it and it will be solid.