What are your best practices for choosing contractors?

[James McGovern]

I always steer clear of Angie's List, Yelp, BP Vendor, Dave Ramsey Select Vendors, or any other service that charges the vendor for membership and then promotes the list to the public as if trust, excellence, and performance have ANYTHING to do with the list selection. 

I also avoid contractors who have dedicated sales people who drive logo wrap vehicles.

I tend to support diversity where contractors who were born outside of the United States or were Veterans in the Armed Forces have worked out best for us.

What are your best practices for choosing contractors?