Rotate your workouts, do presses with dumbells one workout, another do military press behind your neck, and do them in front of your head. Changing it up will allow you to hit different areas of the muscle. I like to do 2 sets in front of the head and two behind the neck. I also been doing drop sets and seeing more development in my shoulders. Just always change up your exercises and try some drop sets. Best of luck.
Mike