Meters, Volt & Amp

I'm in the process of building a DC H.O. layout. I've read that volt and amp meters are a good idea. However, what do they tell me when I run a locomotive? How do I wire each in? Any and all help will be greatly appreciated, as I've been on the Internet for over an hour and can't find anything that explains exactly what information these meters provide when connected to a DC model railroad layout. Thank you.

Got a short? The current goes high.
Dirty Track? The meters flicker back and forth.
Loose joints? Meter flicker or current drop.
Motor overworked? The current will slowly rise. Warning! Shut Down NOW!
Want to measure performance of one or more locos? Meters do it.
Running more than one loco in a doubleheader? Watch the performance.
Want to know why you are blowing headlamps? Are you running the voltage too high? The meters show it.
With a center 0 voltage meter, you can tell the direction of the loco/block switch settings.

Does this help?

Thank you Roger. That explains what the meters do to indicate a problem with either the track or an engine. I appreciate your help.

another use for the meter is when you are wiring up the layout you can see where the voltage drops along the track so you know where to put in booster wires to bring the power to the distant tracks from the power pack.

I found that was a great help in making sure the power was equal around the bigger layouts I have built. before i got my meter I was always guessing where the extra power leads should go. wasted sometime putting them in only to find out they were needed else where.
also the meter can be used to check the current levels coming out of the pack to make sure it is not too low or too high to run your fleet.

i got a digital meter easier to read and to under stand. good luck and enjoy
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For checking voltage, the meter should be wired in parallel with the tracks. For amperage, it should be in series.