Print business cards. DJs are often hired based on referrals, and you can increase that word-of-mouth revenue by passing out aesthetically pleasing business cards at every event you work. People remember a good DJ, and if they have your card, they'll pass it along to someone who needs it.
Send press releases, printed on your own letterhead (using the same design as your business card) to businesses and schools to make them aware of your DJ business. It's not every day that businesses and schools receive emails and press releases about DJs, so the next time they need music for an event, there's a good chance they'll call you.
Build relationships with wedding and event planners, caterers, photographers and other event professionals. Get your name on as many recommended vendors lists as you can. These are lists of clients that wedding planners and venues strongly recommend that customers use for their events. Vendor lists are used frequently, so getting your name on as many of these as you can could bring you lots of business.
Utilize social networking sites. Gaining a strong online presence on sites such as Twitter, MySpace, Facebook, and the like will put your name out there for people to remember. Mention people you've worked with in the past, who can be great referrals for your business because they'll remember the good job you did for them and will want to pass along your name.