Late last fall one of my neighbors pruned his azaleas into perfect little spheres. While these groomed orbs looked great all winter long, in the spring their blooms were less than impressive. You see with azaleas, the blossoms start to form in early summer. If you prune too late you are cutting off next year's bloom.
The simple rule of thumb for azaleas is to prune prior to June. Unfortunately it is a trade off. You have to decide whether you want perfect little meatballs, or are the blossoms the reason you grow azaleas.