Like, like, LIKE! Joe, you give excellent troubleshooting tips and I totally agree with your advice regarding the ground wire.
There is one more 'trick' in my bag of electrical tools. I put a light bulb in series, in the 'power' wire. When checking a motor or other device, if it has a direct short to ground the bulb will shine at full brilliance. What size bulb? I have used a sealed beam to actually see current as it passes, in the form of light. If the circuit is good a larger motor will show light in variable degrees. At first, the bulb will be bright, then the light will tone down and when the motor stalls the light will be bright again.
Incandescent light bulbs raise their resistance as the heat raises. So when the light is dim, or cold, resistance is low (like the bulb isn't even there). I first saw this 'automatic variable resistor' used in a Motorola tube radio. At first I didn't understand the function. Then I stood in awe at the simplicity, cost and engineering brilliance.
I also use this light when chasing unwanted short circuits that pop fuses: Leave the fuse out, connect the test light to +, then connect the light end to the 'bad' circuit. Let the light shine and start unplugging connectors until the light goes out. Eventually you will get to the short. - Dave