Ground the amp to the FRAME, install a cap of sufficant size for the amp your running, use good quality wires, check all connections, and make sure seperate your wires (power and signal).

Sorry if all that has already been said, didn't read all the post. Should help you out.

*Edit*
If you are running a very high powered system, you might want to consider upgrading your amp, battery, or both.

 

he may be a **** stick but is true u dont ground to a battery, im an electrical apprentice and ground to your car!!