There are a couple of differen't routes that you can route your cable. I ran my cable thru the big hole on the firewall (passenger side) and routed it underneath the rug (Remove the Scuff Plate To Route Cable) right against the unibody were it can not be seen or felt. Continue under the rug and under the back seat (You will have to remove the lower seat) right into the hatch or trunk and hook her up. Take's about 10 min. The cable stay's nice and protected as it's in the car and it's the shortest route which is an advantage as well. (Less Weight, better current etc.)
run all the wires that go to ur battery under the hood to ur trunk.....best idea would be to run the wires to where the battery would be going in ur trunk.