Butt Connectors
These little guys should be your best friend. These are the most rock solid way to terminate a wire into another. Simply insert your two wires into either end of the connector, and crimp each end really tight. These connections are the most popularly used in stereo installs due to their reliability and durability.

Distribution Blocks
When you need to rout some power cable down the chassis of your car, use a distribution block to spit off your connections. If you are installing multiple amplifiers, run a main power wire to the location they are mounted, and use a distribution block to properly downsize and split your main power cable.

Heat Shrink
One of the most important things to do when making wire connections is ensuring they will not come loose. You do not want your connections making contact with any other wire or bare metal on the vehicle, unless you want a fireworks show in your car. Heat shrink is very important when using ring terminals on large power cable, and also when running wires through and around your engine bay.

Sound Dampening
You don’t need to go crazy. Sometimes, all it takes is the use of a little sound dampening material on your license plates and behind each speaker to drastically reduce vibrations that naturally occur during your thumpin’ music. Use as much or as little as needed, but never overlook this material. If you find that your car has more rattle than a lance-headed rattlesnake, then it’s time to go shopping.

It is important to not strain any portion of your electrical system. Relays can be used to create a switched 12v positive power source that is hard wired directly to the battery. In fact, you can run almost all of your accessories off a relay. If you have multiple accessories that are triggered on by your car stereo’s remote turn-on wire, it will only be a matter of time before your components start malfunctioning due to too much current draw on your head-unit.

Fuses & Fuse Holders
Be sure you fuse every power wire for every accessory that is added into your vehicle. Nothing would be worse than having one of your electronics short circuit, and cause a fire within your vehicle. There are many different types of fuse holders for every gauge wire.

Split Loom Tubing
For bundles of multiple wires, use split loom tubing to make a “group” of wire that is easily manageable, and easier to look at. Split loom tubing helps with organization of wires, and with the use of zip ties it will protect the insulation on your wires from things like heat, corrosion and sharp corners or screws.