The area in which you live wasn't clear to me.

Generally, it is recommended that people find contractors through others who have had similar work done. Obviously, we don't always know other people who have had such work done, but you could ask each contractor for references.

It is also generally recommended that contractors be paid for only a portion of the work, with the the balance of what is owed paid upon completion.

You could try looking for licensing agencies or other sources in your area that may show complaints about contractors. Sometimes that doesn't guarantee finding someone who is good, but it may screen out those who have been complained about too often.

www.pathnet.org has some ideas about selecting a contractor.