A local real estate broker who is familiar with the area and business locations can be a great asset in your search. Be sure to find out what fees and commissions they require.
You can also hire research firms to provide information such as demographics, traffic, projected growth, etc. This can be very valuable in locations that are very competitive or quickly growing.
With a bit of research, and perhaps some outside help from these resources, you should be able to create a short list of three or four locations that look promising.