This is not quite a built-my-own kinda thing, but it is a how to and my first post in the JK section got out of hand prior to it even starting so I'm doing one here.
In this project I used this tap from Quadratec:
Quadratec Exclusive JK-APT - 12 Volt Power Adapter for 07-11 Jeep® Wrangler & Wrangler Unlimited JK - Quadratec
The instructions that came with this left something to be desired for me. So, I just figured it out. If you read all this, you won't have to.
After you order the above, you need a 7mm socket and a small standard screwdriver. You also need all your wiring, a switch, lighting and your relay system.
Here is a good relay with the wires, and they already have terminals on them. not bad for $12. Available from O'Reilly's Autoparts.
We are going to be removing the lowest portion of the center stack on the dash. Mine has a little net on it, others may just be blank.
If you have an auto, I would recommend putting it in 1, so the shifter is out of the way. You should also put it in 4L so the Xfer case selector is out of the way.
I just started pulling on the top left corner of the net, and the cover started coming off. It seems to only be snapped in on top. If you have the blank cover, you could just pry the top off.
Remove the cover.
Remove the two 7mm bolts located just below and to the outside of the power outlets. In this pic they are still on the dark plastic, not on the lighter grey plastic.
Remove the AC vents. you can do this by grasping the vents ciricular ring and rotating it until it becomes loose, then they simply pull out.
Pull the center stack out by the bottom, slowly but firmly.
Here is where you make a serious decision.
If you want constant power, you need to tap the power socket on the right hand side. If you want power that is only on when the acc/power is on tap the left hand socket.
**NOTE: I do not know which wire is which for the constant power socket. If this is the side you want, you need to find a wiring diagram with colors so you can see which witch is which**
I wanted power only when the vehicle is on so I chose the left hand socket. Pull the plug out of the back of the socket. There is a tab that you must press on the passenger side of the white plug.
After you pull the plug out, you can put the the clips on the wires, they really go on one way, but basically you put the wire in the groove in the metal part of the clip and close it with a pair of pliers.
**NOTE: The blue wire w/pink stripe is positive and the Black wire is negative**
Plug the harness wires into the the sockets. Red goes to blue, black to black.
Now you can plug the socket back in to the power outlet.
Pull off the top cover of the center stack. This can be done with a screwdriver in the corner near the windshield, one on each side. Simply put end of the small screwdriver in and pry the cover up.
Remove the two bolts holding the center stack on at the top. I have already taken them out in this pic, but you can see where they were.
Pull the center stack out, just enough to route the wires up to the top where the open basin is.