It could be worth your time to give away a few free details. Find a local club or organization raffle and donate a certificate for a free detail. It is a great way to get word of mouth started. Give the people a reason to talk about your services and they will.
Another hint... drive around town and find out who is selling the large and expensive houses. It's easy because they usually have their name and face on a sign in the front yard.

Many real estate agents drive a lot and their vehicle is a part of their professional appearance and are great word-of-mouth spreaders. Offer a free or discounted detail and try to get onto their "Welcome to the Neighborhood" packets.