Take hold of a suitable weight dumbbell and lie sideways on a flat bench, propping yourself up onto your elbow so it is perpendicular to the bench. The dumbbell should rest sideways on your upper thigh. This is the starting position.
From the starting position, raise the arms upward keeping a slight bend in the elbow and breathing out as you lift. Pause at the top for a second. The "top" of the movement is when the shoulder joint is at a 90 degree angle to the body (for a larger range of motion, you may start the dumbbell either just in front of the thigh or behind the glute).
Lower the dumbbell back and down to the starting position.