Use your opposite fingers to slightly stabilize your elbow and cue you about the correct position of the arm. (all-about-arm-exercises.com)
Do them with your arms straight out in front of your chest, with an overhand grip, the starting position of the arms being at shoulder width. (fitnessandpower.com)
The passive positioning of the arms and legs help with centralized drainage of lymphatic fluid. (t-nation.com)