The overhead press is often performed incorrectly because of the high-degree of shoulder stability and mobility required. Improper technique not only leads to poor performance, but also shoulder joint misalignment and pain. However, performed correctly, the overhead press is great for developing stable, strong and healthy shoulders. In the video, notice how my body remains straight (no arching back) and the bar travels close to my center of gravity. You will also notice how much range of motion my shoulder blades have to complete. It is helpful to move slowly and focus on stabilizing the torso and upwardly-rotating the shoulder blades.
In most people, the deltoid, pectoralis, and upper trapezius muscles are dominant, while many of the muscles that balance these muscles are weak (especially the ones that pull the shoulder blade down, and upwardly rotate it).. Commonly, this will be evident in poor posture at rest. And even more evident when the arms attempt to press overhead.
To press overhead properly, a trainee needs to understand proper shoulder mechanics in order to control the shoulder joint and shoulder blades. They also probably need more work to strengthen the shoulder stabilizer muscles. I regularly use a couple exercises that work well for this: the Inclined Scarecrow and the Inclined Stick Press (see video). These exercises work well, because they are able to challenge the shoulder stabilizers more than the shoulder prime movers (deltoid). Also, I am able to cue clients to lock the shoulder blades back by "puffing their chests out", and "bend the stick around your head like you are bending it against your forehead." These coaching cues help the client to activate the proper muscles and add stability to their overhead press.