Where practical try to visit a showroom or view other work carried by the contractor. Alternatively ask to speak to other clients on the unit. Do bear to mind however that the company will to give you reference that be free. Try and ask specific questions for instance - Did they increase on experience? Was any thing missing and how much quicker was this rectified? Did they leave the site clean and tidy? Don't always expect "perfect answers" - in fact be suspicious if are usually. Any type of building work or remodelling get a its problems or unforeseen challenges. The actual is "how quickly was it sorted and was it to your satisfaction". It's often been asserted that the true test associated with company happens there are problems - not when everything goes perfectly.