Use a fuse tap and piggy back off of a live fuse in the interior fusebox.
I was thinking more of a discreet wire tap.
What are you trying to do?
Don't forget constant 12V power to whatever you're installing means a steady drain on the battery unless that device has a switching circuit, in which case you'll need ACC 12V power anyway. Also note that note of the dash wires should have more than a 5amp or so draw, so don't try and wire an amplifier to your clock pod wiring, for example.