I was very lucky to have been taught this very early on in my career. It is the proper approach to begin almost every repair situation. The three C's are, The COMPLAINT, the CAUSE, the CURE. For instance, a customer comes to you with his automobile and says, my left headlight is out, I need a new bulb. This is the COMPLAINT. Now the technician needs to determine the CAUSE. Why is the left headlight bulb not illuminating? MAYBE the filament in the bulb has broken, maybe the wire to the back of the bulb has been chewed through by a chipmunk, maybe the fuse is blown, maybe the bulb has fallen out of the socket and is dangling in the engine compartment. I have seen all of the above. Before you walk to the parts counter, you must determine the CAUSE of the problem. Only after you do this, can you state what the CURE will be. That was an easy one, here is another. The customer states that when she applies the brakes she hears a loud grinding noise from the left front. You remove the left front wheel and see that the outside face of the brake rotor is grooved, and the outside brake pad is worn to the metal backing plate. You have found the cause of the noise. What is the cure? An experienced technician will know that his/her diagnostic procedure is not complete until he/she looks at the the right front brake assembly. The other side may be just as bad as the left front and the driver just wasn't hearing the grinding from that side. Or, the other side may present brake pads that have 75% lining remaining and a beautiful rotor. So now, you have not yet determined the cure for the problem fully. Upon more diagnosis, you have found that the left brake caliper outer piston is not retracting and because of this, it has caused that outer brake pad to excessively wear and damage the rotor. But why did this happen? Since you are an experienced auto technician, you know that brake caliper longevity is directly associated with proper brake fluid maintenance, so you look in the brake fluid reservoir and find ugly brown sludge. Now, you have much more information to help you determine the cure. The lesson here is that there is a proper approach and sequence of diagnosis when approaching any automotive problem. And many other problems in life too.