[piecesparts]

The trigger wire for the amp can be a 16 gauge wire. This is the one that is run from the back of the radio unit to the amp to turn it on when you turn the radio on. There are two ways to wire the amp from the radio for sound. The first is the best (cleaner sounding signal); it is by using RCA cables that send a low power radio signal to the amp. If you only have right and left to worry about then there will only be two. If you are going for front and rear seperation and the right and left sound, then there will be four cables. Hopefully the radio is set up for this.
The second way is MOST radio/head units have a set of higher power speaker wiring connections, along with the RCA connections. This is usually around 25 watts and can be connected to another amp. However, this may created a distorted sound when you try to increase the power the amp is capable of generating. The signal is confused by the power that the radio unit is sending out. This is not recommended.

Most head units have a wiring diagram in the back of the owners book that shows the simplicity of how this can be hooked up and what color wire goes where.

The power wire for the amp needs to come from the battery through a fuse or circuit breaker and connect to the amp directly. It needs to be whatever the recommended size that the owners manual has. Most are around 10 gauge or 8 gauge. The fuse needs to be just after leaving the battery---so that if the wire were to rub through and "go to ground" your truck would not burn up. Where ever you go through the firewall or sheetmetal, drill the hole big enough to use a good quality rubber grommet for the wire to feed through. Safety is first. I personally run all of my stereo equipment ground wires to ONE point (radio, amps, or accessories) so that there is no ground static build-up in my sound. That will be your choice, most people ground to a clean sheetmetal point that uses the frame to feedback to the truck battery, at different points in the body.