Before contact with your ex boyfriend begins again, you'll need to have laid totally low for a while. He'll need to understand that you've accepted the break up before he'll want to speak again - otherwise it'll be too awkward for the both of you. Time heals all wounds, but using this to your advantage it can also help heal a breakup as well. Once you've learned the ways to make him miss you, and once you've taken away his relationship safety net, he's going to really start wondering what you're up to. This will lead to contact, and if you play your cards right, he'll probably be the one to reestablish it.
Talking to your ex may be easy, but saying and doing the right things is not. When contact first occurs, you're going to want to be very careful with how you speak. Take it slow, and keep the conversation light. If possible, let him do most of the talking. The biggest mistake most women make when their ex calls them for the first time is to show too much excitement. This gives away your position, and it puts your ex-boyfriend at an advantage because he'll immediately know he can get back with you whenever he wants to. This isn't what you want right now.
Instead, you want to keep up the air of mystery surrounding you these last few weeks. While you still love him and want him back, you should have him (for the most part) out of your head each day. You should be having a great time without him, seeing friends, and generally "moving on". This worries any man, even one that ended the relationship himself. It makes him wonder that if you're this special, why did he break up with you in the first place?
When speaking to him, maintain total control over your emotions. Don't tell him you miss him or that you've been thinking about him. Try to be friendly and nice, but at the same time, also be a little noncommittal. He might ask about your current dating situation, and this is a good sign. Be honest, and don't embellish. You don't want to talk too much here, and it's best to let him create most of the conversation. Even if it's nothing but small talk, just speaking to him again is a big step on the path to getting back together.
The worst thing you can do here is discuss the break up. Don't do it. If he brings it up himself, simply tell him that you wish things didn't end the way they did. This one important line will unlock the door to the relationship for him, letting him know he's clear to try to open it again. But your casual attitude and demeanor also let him know that he's going to have to open that door slowly.
If your ex hasn't called you by now, don't worry. There are other techniques you can make use of on your end that will influence him to initiate contact. There are also good ways to get in touch with him for the first time after breaking up, without putting yourself in a lesser position. Try to think of a reason you need to call him, or maybe a bring up a mutual friend you recently ran into.