School me on wiring

One thing I do that helps a lot and saves a lot of time is to make a folder on my computer for each specific vehicle I deal with.
Then everything I look up or download for that vehicle goes into it's specific folder (even internet shortcuts) if something is read only, I will use screen shots to save images that apply to what I am doing and/or copy and paste text and images to a word processing program and save those files in that car's folder.
Then when I'm done with that vehicle I burn all that info onto a CD and put it away, or send it with the car when it leaves.
That allows me to have any and all information available right away when I or the next owner of a car needs the resource.
When I add something to the car I draw up a wiring diagram for it and stash it in that folder.

There are a ton of excellent resources out there on the internet, but it does take a bit of experience to tell BS from good info.
In the cases of people who are not comfortable with the operations of computers and the Internet, books are the next best thing.