When you need construction work done on your home, business or are having on built, do some research first before you hire a contractor.  Of course you can check the Better Business Bureau:

http://bbb.org

But you should locate your State's Construction Contractors Board such as this one for the State of Oregon:

http://oregon.gov/CCB/

Here you will find all kinds of information along with a watch on the latest scams.

Also, always ask for the contractors license number and validate that license before you hire!