They focus on a handful of core geographic regions, so they are able to announce upcoming openings by announcing them first to existing customers in other parts of the same general region. The cost of this part of the program is low since you are providing the advertising space on premises. Only printing costs are incurred, so a few thousand dollars at most. The effectiveness will be in part determined by the proximity of the new location to the existing one. Another element of pre-promotion is at the site of the new location. While this is under development, the opportunity should be taken to plaster the site with signage announcing your imminent arrival. In my neighborhood, a new coffee shop and steakhouse are opening soon and both have made sure to have large, visible signs in their windows to alert passersby. As the brand's reputation grows, this strategy increases in effectiveness, as evidenced by Krispy Kreme during their rise to prominence. With a highly developed brand, they were able to open new stores successfully relying on this strategy alone.

The third aspect is the advertising itself. Brands may not be built with a short-term advertising blitz, but it will be required to get the first customers through the door. Information regarding new restaurant openings is typically disseminated through print media. These ads can cost upwards of a thousand dollars to prepare and place. But they reach the target market if placed in Entertainment, Food or Living sections of newspapers...

The ads should focus on product differentiation - your restaurant has built a reputation for something in its original market and that should be communicated to the new market. If you consider Porter's three business strategies and Five Forces, differentiation is critical to developing new markets in a competitive field. As a new business, you can use the differentiation to increase your bargaining power with your customers, but should also use some form of discount or promotion as a hook if you are operating a low-cost model.
The ads should run for a month or two to ensure multiple exposures to the target market.

The three-pronged growth advertising strategy will cost in the range of $10-15K per new location. By targeting key influencers, however, sufficient business should be generated to ensure a successful launch.

References

Wansink, Brian and Ray, Michael L. (1993). How Expansion Marketing Affects Brand Usage Frequency: A Programmatic Evaluation. Marketing Science Institute. Retrieved May 12, 2008 at http://www.msi.org/publications/publication.cfm?pub=368

Porter, M.E. (1980), "Competitive Strategy: Techniques for Analyzing Industries and Competitors." New York, Free Press.

No date) Restaurant Public Relations Builds Credibility, Restaurant Advertising Breeds Skepticism. Quantified Marketing.com Retrieved May 12, 2008 at http://www.quantifiedmarketing.com/learning_center/pr_advertising.php