Silvery - 6:58 pm on Jan 28, 2008 (gmt 0)

You need good rankings in Google Maps in order to be in the top ten one-box results appearing on their regular web search results pages under their Universal Search page format.

The two main factors to get good ranking in Google Maps for your biz listing are: location near to the search area centroid, and high user ratings.

As others here mentioned, if you aren't already near the centroid for your area's most common searches (in most cases, you'd want to be near the center point of your town, or your major metropolitan area's main city). If you're not, you could indeed get a post office box located closer to the center -- I'd actually recommend you use a mail store for this rather than public post office, because you're more likely to get a real street address which Google would be more likely to use for pinpointing purposes.

One thing to note if you do get a post box address: if you're keeping your existing street address elsewhere in public directories, you could be diluting out your potential ranking factors since they'd start being focused on two separate listings rather than just one. Something to keep in mind!

The other big factor is ratings -- it's beneficial to have numerous, positive ratings from a variety of business directories. Google pools a number of yellow pages and other directories' information into their Map listings, and the compilation of positive ratings helps them to select which are the top ten listings for any given area search.