1. Don't fall into old patterns: Make sure you both really believe things will be different this time around and you won't fall back into old patterns. The last thing you want is for your relationship to be exactly the same as it was the first time you two were together with the same problems arising.
2. Take things slow: You can't rush love. Take things slow and don't hurry right back into a full-fledged relationship. There is a reason why things ended badly the first time around. Take time to work out all your issues so during the second go around, your bond will be much stronger.
3. Make sure you are getting back together for the right reasons: Think about the other aspects of your life and make sure you are getting back with your ex for the right reasons. Rekindling an old relationship will not solve all of your other problems. It is not beneficial to get back with an old flame just because you are lonely or because things aren't going well at work. Before getting serious, make sure you are getting into a relationship with your ex because you actually want to be in a relationship with that person and not for some other reason.