Cool resource on testing auto electrical systems...
 

Stumbled across this while searching for something else...

"Testing Electrical Systems with a Digital Multimeter

"Perhaps the most important tool you'll use in troubleshooting auto electrical
systems is the multimeter. Basic multimeters measures voltage, current and
resistance, while more elaborate multimeters, such as the Fluke 78, or Fluke 88
have featues that can check things such as frequency, duty cycle, dwell, make
diode tests, and even measure temperature, pressure and vacuum."

http://assets.fluke.com/appnotes/aut...e/beatbook.pdf

Of course, they list Fluke meters, but most tests will work with any DMM.