Of course the first thing I try to do is, maintain excellent service, and product.  This will get you word of mouth promotion, but it is a slow process.  To speed up this process, I try and make one or two of my products outrageous to a point where I am the only place you can go to get this item or service.  Theses are not "promotions", they are things that make your business model unique.  A "wow factor" that people remember where they saw or received a service or product.