1) Make sure that you select a licensed contractor. 2) Make sure to get references and actually check them. Questions to ask:  Was he on time? Were they pleased with work? Did they willingly make any necessary corrections as needed?  Does the contractor have workers compensation? Does the contractor have liability insurance? 3) Get at least 3 bids for your project and do not automatically accept the lowest bid. Check that all bids have the same set of specifications. Make sure that every detail of your project is put in writing. Do not sign anything until you fully understand what services will be rendered and what  materials are included. The estimated date of completion should be in writing as well. 4) A higher priced estimate might be worth it if the materials being used are of higher quality or the materials and labor include a better warranty. 5) Ask to visit the contractors showroom / shop to see work that may be similar to yours. A fly-by-night company will be hesitant to bring you to their shop and will probably not have a showroom at all.