Most Helpful Girl
Well, why did things end? Have those issues been resolved?
If you two are on good terms, then that's a good sign. But you really need to make sure whatever it is that caused the breakup is not going to happen again. Or that you two can work past it.
If you are in friendly contact, then just try spending time together again. Do things that you both think are fun. Bring that fun back into the picture. Then kind of flirt with her and see how receptive she is. Then if you both seem to want to be together and things are going great, then maybe ask her out again?