Most simple way... an add-a-line fuse adapter. They're around $4, I used one for wiring some fog lights. Here's a photo explanation of how one is used along with info about how I wired my fogs. The adapter takes the place of a fuse, the fuse that was once there goes into the bottom slot, and the fuse that will give power to the new accessory goes on top. Just connect the wire coming from the adapter to the power wire of the accessory and there it is! I plugged mine into the #6 slot which is given power only when the key is in the on position. I also wired in a switch in case I wanted them to be turned off while the truck was on. All done!
