As a rule, marketing for legal firms is best summed up in two words: relationship building. A person who knows and trusts you is far more likely to become your client. Once they have done business with you, they are likely to keep coming to you (and referring their friends) for their legal needs.
Getting to know people is easy, but how do you get them to trust you? Of course, the most important thing is to always be ethical. Beyond that, education is the name of the game. By consistently and respectfully educating potential clients about your practice, your legal specialty, and how it affects them, you will demonstrate your value to them and show them that you are competent at what you do.