Word of mouth is the best advertising out there. I work for alot of interior designers. I kick them 10% of the project, and the work just keeps rolling in. A happy client will tell all their friends. Just show up on time, deliver what you promise, and give them good service. At the end of a big project, I send a gift basket with some DVDs a bottle of wine, and if the client has children, a kids DVD. Its a small gesture, but the clients tell EVERYONE.