No matter what side of the breakup you're on, you should make the best of your new role as his ex.
Not to put too grim a spin on it, but it's a fact that most relationships eventually end, and most of us have been on both sides of the breakup equation. Here's a brief guide to handling being on either end—the dumper or the dumpee. The Frisky: 10 Reasons Not To Delete An Ex's Number
When they did the dumping...
1. Maintain your dignity. This can be rough, especially if your split came out of the blue. The fact is, it doesn't have to make sense to you. When someone tells you they don't want to see you anymore, that's not something you can argue. (Not that I haven't tried.) Breakups are rarely a unanimous decision. Badgering him only makes you look pathetic. The Frisky: What's The Worst Thing You've Done For Revenge After A Breakup?
2. Realize that "closure" is a myth. "But it doesn't make sense he dumped me because he didn't like my laugh!" you protest. No, that doesn't make sense. But by digging for "real" reasons you might find something even more hurtful. Then again, he may just loathe your cackle. Either way, who cares? Shut the door and move on.
3. Embrace your inner not-cool girl. Men in particular seem to have an aversion to being the bad guy. I can't even count how many times I've had a paramour pull out the "but I still want us to be friends" card as he was busily wiping his bum with my tattered little heart. You don't have to hate your ex, but nor should you feel any obligation to move straight to the buddy zone if you're not ready.
4. While you're embracing your inner not-cool girl, smack your inner stalker upside the head. In the olden days, you had to actually leave your house if you wanted to get nosy, but between Facebook, Foursquare, Twitter and a zillion other sites, technology just makes stalking so easy. Resist! There is absolutely nothing to be gained by discovering his Farmville status or pouring over photos of his engagement party.