The first thing you are going to do is to hang out with your ex boyfriend’s or girlfriend’s friend. There’s always that one friend that got along with you quite well and who would be willing to stay friends with you even after the break up. And by the way, don’t flirt with this friend, this is not for that. Go out for a dinner or a movie with this friend if possible, but if the friend is reluctant because of your ex, then just start with friendly phone calls and that will suffice.