Multimeter use questions

[SOP8920@Siena.edu]

Hi folks,
   I recently installed a aftermarket stereo in my Q. Although I love the
stereo, I want to open it all back up and connect the dimmer and switched 12v
leads. 
   Andrew Duane has given some useful information. I'd like to combine that
info and test the leads from the car with a multimeter before I connect them.
I am a novice with the multimeter, and would like to protect both it and the
car from any damage. 
   If anybody has some information/tips for me on using a multimeter to figure
out automotive wiring, could you please respond? Thanks!
                               -Osman Parvez
                                89 200q (157K miles)
                                Siena College
                                Albany NY