Check for a permanent place of business, telephone number, tax I.D. number and, where required, a business license.
Request verification of professional liability insurance.
Look for a company with a proven track record; ask for and check client references and request a list of completed projects.
Verify whether the contractor is properly licensed or bonded.
Insist on a written proposal. The proposal should include complete descriptions of the work and specifications, including approximate start and completion dates and payment procedures.
Check to see if the contractor is a member of any regional or national industry associations, such as NRCA.
Call your local Better Business Bureau to check for any complaints that have been filed.
Have the contractor explain his project supervision and quality control procedures.
Carefully read and make sure you understand any roofing warranty offered; watch for provisions that would void the warranty.
Remember, price is only one criteria for selecting a roofing contractor. Professionalism and quality workmanship also should weigh heavily on your decision.