Here is a good video on how to use a volt ohm meter. He explains in one example how to test for continuity. (circuit has little or no resistance between two points)
This is very important when troubleshooting a circuit. One example is you might find " a short" which means the same thing as no resistance. And you may find it where you shouldn't find it. You will know this either by experience or by looking at a wiring diagram/schematic.
Let's say you know by looking at a circuit board that a capacitor is between the input jack and the first part of a circuit. Since a capacitor blocks DC but passes AC and you hear your meter's speaker or see zero ohms by placing you leads on each side of the capacitor. This could be a clue why your amp is not working correctly.
Watch this video, he will touch on the different parts of the meter and what it does.
At the end of the video he suggests getting a Fluke meter. I would definitely second this. Even know a cheapo from the hardware store will work in a tight situation.
Think of your repair gear like having good music equipment. Sure, you can show up at the recording date with a cheap guitar with bad keys and get it done. But you know if you have a quality guitar with good tuners, you will be able to concentrate on your recording, not your equipment.