I just ran into one of my cousins at our local bagel shop (breakfast is the best time and place to meet people and get some early morning work done). He's a podiatrist (foot doctor) and tells me the best, most effective method he's used so far to reach new potential patients is through direct mail.
He goes after a specific market segment -- people who have recently moved into his area. These people haven't set up a doctor-patient relationship yet. So he figures (rightly so) that new move-ins are the best prospects for a podiatrist. He's also interested in runners and older patients -- both have their own unique needs. But his best source of business still comes from new movers.
Thinking this over, I contacted some other doctors in my area and found that when a practice serves a general clientele rather than one specific specialty, people new to an area are good prospects as new patients. There was a tendency, however, to favor new homeowners over people in apartments. This was especially true for dentists who need to develop a several-year relationship to offer effective care and, to put it bluntly, make some money from a stable patient base.
Fortunately, these lists are all available, and even selectable by age, income, and, if it's important to your marketing, a presence of children in the household. Cost for this type of list averages 6 to 8 per name, and less in large quantities.
Another possibility, but one that is usually too expensive for small offices, is the phone company's phone book ride-along program (check with your local phone company for availability). Whenever a new phone is installed in a home, the phone company delivers a new set of phone books, wrapped in plastic or placed in a mailing bag.
Costs are reasonable (usually less than the cost of renting your own list) but you generally have to commit to a minimum 10,000 delivery or more in your area, and you have to cover the entire delivery area. If you're only trying to reach a small area -- such as one or two zip codes -- the phone book ride-along program is not for you. Renting a targeted list and mailing to them yourself makes much more sense.