The most important thing you can do is accept with the break-up because as long as you're fighting against his decision, you won't be able to work towards getting him back.
 You are asking desperately, "What should I do to get my ex boyfriend back?"  Remember, no situation is hopeless.
 Every day, couples get back together regardless of the situation.
 It could be that he doesn't even know himself.
 Maybe he just felt smothered by the relationship and decided that he needed more space.
 Maybe he has a fear of commitment; maybe it's something else.
If you have decided that the relationship is worth saving, then there are steps on what you should do to get your ex boyfriend back, but it will involve a proven plan of action, and some work on your part to make it happen.
1.
Consider why you broke up in the first place - Perhaps you were too clingy, demanding or controlling?  Maybe you even seemed disinterested.
 Any one of these reasons can cause a relationship to terminate.
 If you are asking "What should I do to get my ex boyfriend back?" you need to identify the reason so that you can act accordingly.
Examine yourself and think about what you did and did not do.
 Once you've identified the problem or problems, consider whether or not you are willing to change.
 You can't change everything about yourself so don't even try - rather, focus on the things you can change and will be willing to change to get your ex back.
2.
Be the person he fell in love with - if you are trying to figure out "What should I do to get my ex boyfriend back?" Just be yourself.
 Do not act like someone else in order to be liked - it never works in the long run.
 He was attracted to you because he felt good with you, and you were fulfilling his emotional needs.
 Be positive around him.
 Laugh and smile.
 Always stay positive to feel good about yourself and make friends around you.
 This will definitely take you one step forward in your move to win your ex back.