Here is another great Genealogy Tip of the Day from Michael John Neill. If you are looking at neighborhood, as you can with the census for instance. It might pay to look at first names of those living close to each other rather than just focusing on the last names.
The reason...wives' children may be given the same names as her parent, who may be living close by. You can read this tip in Michael's words and see a sample instance at http://genealogytipoftheday.blogspot.com/