Learn about the materials being used.
Not all roofing products are the same, so be sure your contractor works with a name you can trust. GAF, Owens Corning are the two leading manufacturers of roofing in the country. However just as important to ask about is the other components of the roof, not just the shingles. One sure way to lower costs to the contractor is to offer substitute components like starter-strips, underlayment, Ice and watershield as well as ventilation.
Make sure they are factory certified
Any contractor can claim that they can install a roof. Admittedly it doesn’t require a master’s degree to learn how. However, being certified ensures that installation is meeting the manufacturer’s warranty guidelines as well as building code requirements. Additionally, they are up to date with installation best practices and being certified will ensure you are working with a reputable company as certified contractors are vetted and can potentially lose their certification for poor performance.