A little tip,There is a wire that is 12 volt all the time(with or without key "on" if you have power seats and don't want to tap the battery.Its the seat power wire(soild blue,atleast for mine),located under both fron seats.Its a nice place to tap if you are running accesories,that are not going to pull tons of amps.Its protected by the "30 amp power" fuse.
If you want to run a wire to battery,go through the main boot..just follow the hood release cable,there is plenty of room for several wires to run through....use one of these if you want to be neat,if not some mechanics wire,coat hanger will work as well.
http://www.amazon.com/Thexton-436-Wi.../dp/B000P9IGCA