I found a book at Homedepot that had all the wiring explanations and diagrams in it, even told what would, and wouldn't pass the different codes in some of the big cities. There were several cheaper ones, but I got the $30 one and wired my shed, then had an electrical contractor look at it, and he only made a couple of changes in the box and certified the rest, so it was worth $30 because the contractors wanted over $4000 in labor.