Back when I first started learning this stuff I split with my girlfriend of 6 months, I wanted to stay friends so we met a couple of times slept with her and we almost started dating again until I told her something had changed for the better that used to annoy her. At that point she got really angry with me for not being like that when we were together and she didn't talk to me, then got a new boyfriend.
I would see certain 'Statuses' on MSN that were clearly targeted at me, i.e. 'Never been happier than I am right now'.
After about 4 months I bumped into her and we talked briefly, at that point I also decided she had moved on and decided to move on. 2 months later she messaged me on MSN, we talked for a bit before she asked to meet up. We dated for 2 years after that splitting up while I was traveling, before briefly getting back when I returned but she never seemed to recover from me being able to leave her for a year.
The advice I've read is, break contact, but occasionally have a moment where you see something that reminds you of them and text her (i.e. "Hey just saw 'x' reminded me of how we used to 'y'! Hope you're doing great. Don't ask for a reply, don't expect a reply, don't try to arrange anything. If she contacts you, be aloof, you're just being friendly, you can remind her of the fun you had if it fits with the conversation but don't ask to meet up, don't let her think you want her back, end the conversation first. It has to be her wanting to get you back, she has to feel like you're over her but still friends with her, if she feels that and she wants you back, she'll try to meet up with you.
It also won't hurt to be dating, having fun and improve yourself in someway.