Hundreds of factors have to be taken into consideration when it comes to car audio to achieve a clear, crisp sound. While throwing a subwoofer and amp in your trunk may give you some bump, but what you really want is a BOOM that will make friends jealous and neighbors annoyed!
Step 1: The Wiring.
If your amp is blowing fuses, shorting frequently, or abnormally overheating it is commonly caused from an improper ground.
Correctly ground the amp! Make sure the ground location is excellent. Preferably directly to the car frame, not a flimsy peice of aluminum. Sand the surface, make good contact, yadda yadda yadda. A simple test is a to use a battery tester or a test light to assure 12.6 volts is running through the cables. But a true test is to use a multi-meter set to Ohms and connect one lead to your ground location and somehow connect the other lead directly to the Negative battery terminal, then subtract the natural resistance from the test leads/multimeter. Idealy the goal would be 0 ohms but that is near impossible, just do not allow more than 1 Ohm.
Also important is the guage of the cable. The chart provided is a useful reference tool. The length of the wire and the desired power of the system is taken into consideration.