Get at least five recommendations from people. Go see what was done to their homes. Were they happy with the work? Did the job get completed on time? Will your contractor complain if you pput a penalty-clause in the contract? Ask what other work he's done. Check with the BBB in your area. How long has the guy/gal been in business? Also, get three quotes on the work. Don't buy into the BS that, "Hey, we discovered when we opened the wall there that your electrical conduit needs to be changed and we know a guy who can do it" kinda crap. Last, check with your town/city for licenses (s)he's taken out for other construction and phone them to see how happy they are. Just because a contractor gives you his references, remember that they are HIS refereences.