Casey's answer pretty much nails it, here are a few specific tricks I use to make the process faster though:
Using the moztoolbar do a SERP overlay on the sites for the search term to easily get a feel for the difficulty of competition based on domainrank.
Do a whitespark report to see how many citations the other sites have compared to your site.
Do getlisted.org search on their sites/your sites to get a basic idea of how involved the other sites on the local search are.
Run on page optimization reports for the terms, local and not, to see if you can gain a relevancy advatnage.