Communications is the key. The questions, as you know, is how to do it.
I have a small school, 25 students, a branch of the main dojo. I only teach kids, as that as a restriction my teacher has placed on me, at least until I make Shodan. But over half my students are the results of a single individual spreading the word.
The best advertisement is excited students talking about what they are learning. The feedback I have gotten from parents is that they like my consistancy, no hype, reasonable pricing, and an organization behind me that they can see and interact with.
The biggest boost I had was when my Sensei visited for the first time. Other visits by my classmates was important to show the friendships and cooperation. And I let them see and watch the higher level stuff, so they can see there is more in the future.
The other thing I do is a monthly newsletter. Nothing big, single page, provides some key dates in the future for planning, acknowledgements of milestones and promotions, perhaps a training tip or other interesting bit of history.
Respectfully
Mark W. Swarthout, Shodan