http://www.mmxpress.com/technical/ampinstall.htm
All I did was attach the amp ground wire to a chassis bolt nearby. It's been that way for a year. Do I need to do all of the above?* This is where most people make mistakes. This is important! First, install a ground cable from the negative post on the battery, to the chassis of the car. If you can reach it, it's best to run it to the firewall, since most cars are a nearly solid sheet of metal from the firewall to the trunk. Make it the same size, or larger than the positive cable. I like to run a 4 gauge or larger to the engine block, AND a 8 gauge or larger to the chassis. Don’t be afraid of over kill here. You spent good money on your amps and the rest of your system. Don’t skimp on a 2 foot length of cable now. I use 0 gauge cable on my own car to the engine block, and 2 gauge to the chassis. Near the firewall, I also sometimes add a piece of 4 gauge from the block, to the firewall.* Near the amp, install a ground distribution block.
* Find a spot as close as possible to this, to connect a ground cable. You can connect it to an existing bolt, or use a self-tapping screw, or drill, and use a bolt, and nut. If your gonna drill, make sure you don’t drill into your gas tank! The main thing is, wherever you do it, make sure you sand off all the paint, and put it right on the bare metal. You can use some Vaseline here to prevent corrosion, and rust.
* Now connect the cable from the chassis, to the distribution block.
* Run a piece of cable from the distribution block, to the amps negative (-) terminal.
