1. It doesn't matter if your eventual goal is to get your ex back or not, one of the first things you need to do as soon as the breakup happens is to sever contact completely. If you just want to move on, that may make sense to you...not so much if you're after a reunion, but trust me when I tell you that it's the right thing regardless. Giving the two of you some time and space to organize yourselves and figure out just how you feel is necessary whether you see a future for the two of you or not. If you're after a reunion, this time lets you plan out your strategy, and if you just want to move on this time can help you allow the pain to subside.
2. Take some pride in yourself during this time. Too many people let breakups keep them from living their lives, so what you need to do is keep yourself busy doing things that make you feel better...and I don't mean destructive things like drinking, I mean positive things like building your self-confidence back up. Working over your appearance can actually be a great method for this. Even if there's nothing you don't like about yourself, changing it up a little can bring a freshness to your life...make it feel like the beginning of a new chapter in your life. Besides, looking great all the time will get you some attention from others, which is good for your confidence and can even inspire a little jealousy in your ex.
3. Stay social! Sitting around at home does nobody any good, its just an opportunity for destructive behavior. Besides, looking good doesn't help much if nobody sees you! Go out with your friends and have a great time in spite of however you may feel inside. Even if you're hurting over the breakup, don't let that be an excuse to not live your life. If you just force yourself to have a good time, pretty soon you'll start to realize that you actually ARE having fun...and suddenly life will seem a bit more manageable.
All of these things together serve two to accomplish two important goals: to rebuild your self-confidence and to help you realize that life after a breakup continues and doesn't have to be any worse than you want it to be. You're in control of your own life, and if you give up that control you can still get it back. Even if you're sure you want your ex back, there'll come a point where you can decide for yourself what you want...and get it.