reject any contractor who is not licensed.
do not be fooled by a contractor with a license. Generally, the
license requirements are minimal and the law is generally poorly
enforced. A better test is to question the contractor's commitment
to his trade. Is he a member of the trade association?
Call the association
and verify the answer. Ask if the contractor is taking Continuing
Education Training, similar to other up-to-date professionals.
Ask to see certificates.
A professional contractor
will be only to happy to respond to these questions.
Reject the contractor
who blows off your questions as not being important. There
are probably a lot of other issues he deems unimportant and will
blow off, maybe one being your satisfaction.