Google recently blogged about how local listings work:http://maps-forum-announcements.blogspot.com/2009/06/local-listings-where-do-they-come-from.html
Here are my simple tips:
First: Check the companies that have the highest listings in the local directory under your category (Keyword term). Look at their “overview” on the local listing. Note the web sites Google has listed for them. Go to and list your company at the public sites on the list.
Merchant Circle is a terrific site for this, as is yahoo local listings and best of the web.
Next, get reviews onto your listing! Send an email or letter to your customers and ask them to post a review on the Google local listing.
Then, add photos and videos.
Make sure you are listed in the best category and use a robust description of your company.
If your not in the local directories, add your company here: http://getlisted.org