Below is a step-by-step tutorial on how to properly set your amp gains. You can basically find this information anywhere so I thought I'd make it easier and post it here for those who are new to audio and/or never knew how to set their gains.

In order to do this you will need a DMM (Digital Multimeter) You can get those @ electronic shops or ask your car accesories near you..
For those of you who wonder why your amp shuts off or why your amp/subs die, it's because most people push their equipment more than it can handle. Therefore causing "clipping". To prevent from clipping your equipment, here's a tutorial on how to properly set your gains on your amplifier(s).

To set the gains, use your MAX settings you would normally use. For example if the loudest you listen to your music is 20/30 (Volume on headunit) with bass +2 and treble @ 0 with MX on, then use those exact settings.

**NOTE** Be sure to have your vehicle on while you do this.

It should also be noted that if you want to use bass boost, set it prior to the gains and use the center frequency of the bass boost (45 Hz for most amps) as your test tone. Also, remember that if you have a subwoofer volume control, set it to full before you set the gains on the sub amp.

Here's the formula you will need to use.
Sqrt(Power*Resistance) = Voltage
(i.e. If you bridge a 4 ohm subwoofer to your amplifier that is rated to produce 100 RMS @ 4 ohms in bridged mode, you would want Sqrt(4*100) = 20 volts)

Here's a step-by-step flash tutorial from the JL Audio website.
http://mobile.jlaudio.com/support_pages.php?page_id=143

Test Tones you will need to download & burn.
(50hz is best to use for subs / 1khz is best for speakers)
http://realmofexcursion.com/downloads.htm

Hopefully, this all will result in greater longevity of your products and cleaner bass. Some people still insist on cranking the gains after using this tutorial because it's "not as loud as it was." If you choose to do so, you may be putting your equipment at risk. If you find that the output is too much, feel free to turn the gains down.