Here you go... instructions to make your life easier.
I'm not trying to be anything but helpful...just had a couple drinks is all.
R of this is: Place the black lead of a multimeter set to DC voltage on a bare piece of metal on the vehicle or a known ground (screw head, etc). Use the red lead, and touch it to 1 wire at a time until 12 to 14 Volts DC is indicated on the meter. That is your positive lead.
To find the ground... Set the meter to "Ohms" (looks like the greek symbol for Omega) and again, leaving the black lead on a known ground... touch the red lead to 1 wire at a time until it reads "zero" Ohms. That is a good ground.
Repeat both processes with the vehicle power on/vehicle running. The reason? Modern transistor/logic circuitry in body control modules can simulate "ground" on a power supply circuity when the system is in a de-energized mode of operation.
Also... you can search the website Car Alarm, Car Stereo, Mobile Video, and Cruise Control Info for Installers
(it's an audio installer site) for diagrams/information on your specific vehicle.