After 8 months apart, my ex and I got back together, even after I thought we were over for good. This is just my own personal experience and I don't intend for it to be a "how-to" on how to get your ex back.
What helped? For one thing - and this won't necessarily be the best thing for everyone- we dated other people in between. I didn't go looking for anybody, but I hit it off with a friend of a friend at a birthday party and I decided to give it a shot. It was an enjoyable albeit brief relationship and at the time, I even thought my new bf was even more compatible with me than my ex (I even wrote a thread about it here). That unfortunately turned out to be wrong - I won't go into detail - and to top it off he was moving accross the country for a job. It was an amicable split, and I don't regret it. It made me feel confident about dating again and knowing that there were other great guys out there besides my ex.
My ex and I reconnected after studying for finals together, as we shared two classes. He said he had been thinking about me a lot, and admitted that his decision to breakup was stubborn and irrational. Finally, he said that he wanted to get back together and make things better. I see so many people on these boards trying to decipher "I miss you" messages from their ex - but unless they explicitly state that they want to get back together, take it with a grain of salt.
We were in NC for several months until this point. When I found out he was dating someone, I did not lash out at him and let him know I was happy for him. He later said he was impressed with my emotional maturity. We both contributed to the downfall of the relationship and we apologized to each other and vowed to work on our problems. So far, things have been going well.
What didn't help? Early in the breakup I snooped on his blog, sent him angry texts, begged for him to come back, and made drunken phone calls - basically, all the things you shouldn't do. I read those stupid "how to get your ex back e-books", which are obviously designed to scam the heartbroken out of their money. All of these things pushed my ex away. Overall, I believe that letting go of all hope, going NC, spending more time with friends, doing new things, and genuinely trying to move on are crucial actions after a breakup. After 8 months, my ex and I just kind of drifted back to each other naturally without and ulterior motives or plots to get him back. Even if we didn't get back together, I felt happy and content being single.
Oh, and we recently attended his friend's wedding together. And guess what? The bride and the groom had broken up for a few months before getting back together. She told him she "just wanted to be friends", but obviously down the road she realized she had made a mistake. They even incorporated the story into the wedding speeches..haha.