Good point Jim. Another one to look into are geneology groups/orgs. Now there's a group of people with a lot of old photos and are interested in having the work that we do done!
My approach to referrals is to send out a post card (see Business Challenge #1). I send out my card with a nice little note saying thanks in the hopes they will hold onto the card and pass it to a friend. Or if nothing else it is a little reminder and they think "how nice" and next time they show off their repaired such in such to their friend they may name drop!
At my previous place of employment people would come in with newspaper articles about the business that were 15 years old or anchient business cards and brochures. It's amazing where people dig up a name!
One thing that is important to remember is that people feel more comfortable when they have a word of mouth recommendation. So as Jim said treat the work well, treat the client well, be friendly and thoughtful and do a good job and your previous clients will help you advertise!
Don't forget to keep a mailing list and add your new clients to it. Also ask people when they call or come in where they got your name. It is nice to know who is recommending you. If your business is mainly from the yellow pages you might want a bigger ad. If a certain frame shop recommends you a lot you might drop by and say thanks, send them brochures or cards so they can hand them out instead of writing information on a scrap of paper or send them a Thankyou. Every little bit helps and showing your appreciation just gives you more business.
Just my thoughts on the subject.