Selecting a Contractor

What is the absolute worst way to pick and hire a contractor? Telephone soliciting is a pretty bad way, but in my opinion door to door has got to be the worst. Wednesday I was at my office and had a guy called wanting to sell me leads that he would get going door to door asking people what kind of work they were going to have done in the next six months.

He had no idea what kind of work I do (which is great) but he didn't know that. What's worse is the homeowners have no idea who he would be selling their names to. Now granted some people going door to door are trying to get work for their own company, but how good can they be if that's the only way they are getting work.