The most important question to ask first is if they have insurance. Mistakes can be costly and in the event something does occur you need to feel secure knowing the contractor is insured. Also inquire if the company is a local company. When you are working in construction things do happen and they need to be fixed, if the contractor is not local it is highly unlikely they will come back to make the repairs. Check out the company’s website and see if the pictures are stock pictures or are they actual customer photos. Look up the reviews for the company. A company that does not have any reviews is highly suspect and should be looked into further.