The time right after your ex breaks up with you can be a really difficult part of your life...just dragging yourself out of bed in the morning can seem like almost too much to bother with, but if you let yourself succumb to your depression you'll never recover...and never get your ex back!
The first thing to do is cut down your exposure to your ex...being in each other's faces right now will only have negative effects, as the friction can cause stress and the memories can cause heartache. In addition to avoiding negative effects and problems, limiting your contact with your ex can also have positive effects. It can give you a chance to pull yourself together, and also to start building on a plan to win your ex back.
What you DON'T want to do is fall into the classic mistakes people make when they're in your situation. Most of these are communication based, so just doing the "no-contact" thing will help a lot as far as keeping them from giving you trouble, but not all of them are so easy to spot, anticipate, and ultimately avoid. Many of them are very sneaky, and will disguise themselves as ideas that sound really good at the time when the only thing they'll ever do for you is making your life more difficult.
Another piece of advice is to keep your friends close...their support will help to lead you down the right paths as well as lend you the confidence to pull your life back together and find the easiest way to getting what you want.
