Ok this one is really simple. The best way to understand occlussion on which one is the working and non working side is using your on mouth. Ok let say that you are doing a working lateral movement to the left. Move your mandible to the left slowly as you can feel the left side is more in contact that the right side so the left side is your working side the inside of the facial superior cusp, the inside and outside of the palatal cusp of the maxila and the inside and outside of the facial and the inside of the lingual cusp of the mandible are in contact when you have unwanted contacts you have to follow the movement so if in the a, b, c contact a is the disere contact and as the madible move the cusp should get out contact so if b and c persist you should get rid of them
