I think the best way is to deal with hacks, on top of turning them in is customer edjucation. When walking through for an estimate, of even in any residential situation is to point out poor work directly to the customer, (Find out if they did it themselves.) and laugh out loud! And say, "I wouldn't let that guy in my house again. Even if you don't hire me to this work, make sure you hire a qualified and licensed Electrical Contractor."
Send them to some information: http://www.cslb.ca.gov/forms/Owner_Builders.pdf http://www.cslb.ca.gov/forms/wysk.pdf http://www.cslb.ca.gov/forms/tentips.jpg
Break down the violations, and hazards to them. Explain some of the little nuances, and consiquences, like it removing value from thier home. Odds are, when thier freinds are planning to some work they'll remember the conversation, and talk their freinds out of hiring a hack or DYI.
I personally think some of the mystery and danger needs to go back into our trade. People are getting too comfy with DIY, and Hire-a-hack.