I like to start at the fuse block or at the fire wall.
Loosely lay all of the wires out to there general location (left side of engine, right side, rear etc.). This allows you to visualize how simple it is. Get EVERYTHING straped in place BEFORE you make any connections or cut any wires.
The last thing I do is the final connection...make sure you route the wires so they won't be in the way of items not installed, like exhaust manifolds or pipes. I also like to leave just a little slack just in case I make a bad connection I have something to work with and for vibration/movement.
Also don't forget to install the grommet before putting the wire through a sheet metal hole...
Hope this helps,
Mike B
