Following are a few indicators that you should review thoroughly before deciding on a market. Is there a population growth? Is there job growth? Where there are job opportunities, people usually follow. How are the schools in that area? Crime rates, weather patterns, etc.
There are several useful websites to use to review the stats mentioned above. A great tool is City-Data; they collect and analyzing data from a variety of government and private sources, and provide detailed, informative profiles for every city in the United States.