I just finished my harness and while I don't know if I did it right, some of the things that helped me was:
Label every connector so you know what it does. this helps determine if you cut or keep.
I kept a lot of extras and options like seat heaters, 12V outlets, door ajar switch wiring, AT, evap, and parking brake switch. Some circuits run up the driver side of the body and dash harness, and some up the passenger side. As you get to the thinning where you label the body to dash harness wires, it helps to have the dash there also to see if any extra wires are cut or saved.
Once you thin all the harnesses, you are fooled to think you are close to being done. Russel was right in that you need to settle down into the long haul of extending and shortening wires. A LOT OF WIRES. Wasn't bad and easy to follow the videos, but takes a while.
luckily I see lots of colors
Joe