Poor Posture & Shoulders that Snap, Crackle and POP!
Often times, multiple shoulder movements can cause clicking or popping in the shoulder. While these may be alarming to hear, most of the time, they are relatively normal joint sounds. An easy solution to this is to correct your posture, then move your shoulders around again. Finding the right "alignment" between your neck, shoulder blades, chest, and arms requires a little fine tuning of your own body mechanics but usually once done, will eliminate most of the shoulder noises.
To correct faulty posture, stand up with your arms extended back and palms up, pull your shoulders down and back, release the tension in the upper back muscles, and tighten the abdominals. Try to hold this position 10-20 seconds, 4-6 times a day. (See attached image)
Of course, should you try all these maneuvers and still experience clicking sounds in the presence of pain, it may be time to schedule an appointment. More likely than not, it's a muscular issue that needs to be addressed.