My dad is a doctor and he recommends not doing the military press, or other exercises where you're in a standing or sitting poisition and lifting weights above your head. It puts lots of stress and strain on, and deteriorates shoulder itself as well as the cartilage housed there, often leading to arthritis in early years. If you want to work the shoulder muscles themselves, (posterior, lateral and anterior deltoids) I suggest isolation and other types of compound exercises in which you do not raise weights above your head. Bent over raises, or a similar exercise emphasizing the posterior deltoid, lateral raises, and anterior raises (90˚ bend in elbow, bring arm up as if you're pouring out a beer, still at a 90˚ angle), as well as the many varitations of front raises.