Shoulders are a very complex area of our bodies because they are highly flexible joints that move in many directions. It's important to train them with appropriate exercises, like this one, designed to improve joint stability and muscular balance.
Sit upright in a sturdy chair (you can also perform it standing upright). Grasp a dumbbell in each hand. Begin with your upper arms hugging the sides of your torso, elbows bent at a 90-degree angle and tucked into your waist. Start with the ends of the dumbbell touching at the center of your waist.