I would recommend going to a fitness store for a professional fitting/consultation. Before making a purchase, find out about their return policy. Sometimes what seems like the perfect shoe at the store is decidedly wrong when you actually hit the road.
You could also check the websites of some shoe brands to see if they have a "shoe advisory" - you answer some questions and they give recommendations for what would be the best shoe for you in their brand. (I know for certain that you can do this on the
Brooks website...not sure about other ones. I adore my "Brooks Ghost" for running!)