First and foremost, I'd like to offer my condolences. Ending a relationship is never easy.
I hope that this advice will help.
You're not going to just magically stop thinking about him. A lot of things are going to constantly remind you of this person.
Distraction can really help you. Get yourself involved in a new extracurricular activity. Go get a new part time job. Get a new hobby. Just do something to take up some of your free time. This will help direct your mind away from the past.
If you have pictures laying around of you and him, or things of his still in your house, box them up. Don't burn them or destroy them like so many people say. You can and probably will regret this in the future. Just tuck these things away so that they aren't around to remind you of him. Out of sight, out of mind.
If his phone number is still in your cell phone, delete it. You don't want to be going through your contacts and accidentally stumble across it.
Also be aware that you are probably going to see him while out and about. You should know that his life hasn't ended just because you broke up, and there's a chance you'll see him with other women. Don't let this get to you. Let it serve as a reminder that life does go on.
Take this time to reflect upon yourself and to grow as a person. Invest some more time in friends and family, and turn this negative experience into a positive one!