DML FAQ : Electronics : How can I hardwire accessories, instead of having to plug them in?
All of your accessories should have a hot lead and a ground plus wiring to whatever else they have. All you're interested in is the hot and ground. The question is, do you want hot all the time or hot only when you turn the key on? All your hot leads should go to your fuse or junction box. At that box you can take a voltmeter using the DC 12-volt gauge. You can check your pins in the fuse (junction) box and see which ones are the way you want. Check the pins first with your key off. The ones that show 12 volts or close to are hot all the time. When you're checking the pins your red lead goes to the pin and black to ground. Next check pins with your key in the Accessory position. Then, finally, check pins with your key in the On position. You should be able to wire your accessories accordingly.
As a precaution you should have a fuse in each of your accessories. When wiring to your fuse box make sure you stay on the battery side of the fuse otherwise you could end up overpowering your fuses and having to replace them all the time. You should also have spare connectors in your fuse box. That's even cleaner.