I use a Streetwires (
www.streetwires.com) BT2PF with the built-in AFS fuse holder on my positive battery terminal. From there, I take a 0-gauge wire through the firewall in the only place possible on my car (98 Taurus) without drilling a new hole. Once it's in the passenger compartment, it goes to a Cole-Hersee continuous-duty solenoid that is master-switched by a CarlingTech Contura-series SPST rocker switch.
The other side of the solenoid goes to two fused distribution blocks: a console-mounted 6-position ATO-fused distro block (for powering low-power console-mounted accessories,
www.wranglernw.com catalog page 59), and a trunk-mounted Streetwires CBR44S AFS-fused distribution block (for powering the RF decks and other high-power trunk-mounted accessories).
The ground from the console-mounted distro-block is 8-gauge to a clean-metal hole in the floor. The ground from the trunk-mounted distro-block is 0-gauge to a Streetwires GT0 ground terminal mounted to clean metal in the trunk.
Yeah, I had some hangups at first about using audio accessories in my installation, but I'm quite happy about what they provide, and they've worked flawlessly so far.
The important things here are:
1. Use a sufficient wire gauge and as short a length as possible to avoid burning up your cables and voltage drop.
2. Fuses are IMPORTANT on all positive lines. Some fuse on ground wires. I don't, as it is not SAE-compliant to do so.
3. Grommets, tie wraps, and heat-shrink tubing are IMPORTANT where necessary.
4. Use crimp terminals and spade lugs, but avoid wire taps. Soldering is usually considered better than crimping. In either case, use the right tools for best results.
5. Be sure that all wires exposed to high-heat conditions (such as those found in engine compartments) are rated to handle those conditions.
6. Keep your wiring neat, and don't route wiring where it'll be in danger of mechanical damage.
7. Don't tap the vehicle's fuse block for anything with a current pull greater than about 0.5 amp. Some cars can be finicky even about this kind of pull from the fuse block.
8. Take pride in your installation and *do it right*. You'll thank yourself for doing so.