A. Here's a well written how to page that can take the totally uninitiated or novice, and give them the basics to repair or create the wiring harness that they need.
Comments: What little experience I have in making or repairing wiring harnesses wouldn't really help anyone, although I have become competent at soldering two wires together and using shrink tubing rather than using those cheapo 3M crimp on butt connectors or twisting them and using black electrical tape. This site was recommended to me by "TMIB" from the Chopper Underground forum, so I could pass it along to you.
Additional Information: This is written by John Partridge in Plymouth, England. I recommend following the links on this page and checking out the rest of the articles available from this guy! Everything from how to fix your plumbing to how to build a trike! Awesome site.