You should first ask friends and family for referrals or recommendations. You can then check the online ratings and reviews for these contractors online and on apps like Yelp. You can also check your local Registrar of Contractors and the Better Business Bureau to see if there have been any complaints filed against any of the contractors or companies. Next, check for GAF certification on the GAF website. Finally, ask to see a portfolio of completed projects and find out what their experience, education, insurance, and licenses are.