That clicking and popping you hear is when pressure is applied to your back and a ligament (or sometimes a tendon) slides over a bony prominence on one of your vertebrae. Either way, it's likely an indication for a combination of muscle stretching, strengthening, and probably more importantly - coordination exercise. It is usually not a serious condition, however, for peace of mind, many athletes who experience clicking experiment with particular movement ranges in order to isolate precisely which exercises and ranges cause the clicking, and then avoid these exercies.
Although a painless shoulder click rarely indicates a shoulder pathology, for patients under 25, and don't have arthritis, shoulder clicking is most likely related to instability problems (eg injury from sport, or undue stress from starting a new exercise). When a pelvis and/or lower back is out of alignment, there are usually adverse effects on the neurological system. For example, nerves entering and exiting the spine may be compressed and thus unable to perform their function to the full extent. Circulation and metabolism will be affected, and digestion and elimination can suffer. Legs will be thrown out of alignment, potentially causing long-term chronic knee and ankle problems. So if you are concerned most certainly see a sports physiotherapist, a chiroproactor or at least your local family doctor. For example, a physical therapist would be able assess your performance and advise you on other exercises that may optimize the results of your exercise whilst minimizing the clicking.