Word-of-mouth is one of the least expensive, and effective, ways to promote your graphic design business and land more jobs. There are many ways to encourage it, some of which cost nothing and take little time.
Send a Newsletter: Send a monthly or quarterly newsletter not only to show off your recent work, but to also remind people that you are open for business.
Business Cards: Don't meet that key contact without a way to easily give them your info... design a business card that represents your style and always keep them on you.
Get Your Credit Line: Let people know who designed something as soon as they see it, and hopefully they'll track you down.
Create a Portfolio: It is crucial that potential clients can see you work. Build a website or PDF portfolio that will work for you.
Remind Your Clients: After a job well done, let your clients know you are available for more work and interested in referrals.