I try to be at home to return a call. I get on my PC, draw up Google Earth. When they give me an address, I can look not only where they live, but also something about their property, "... driveway on the left side of the house, right?" "... wedged shaped lot, right?" "... about 200 feet down the right boundary, right?" If the neighborhood is familiar, I know the house.
If I know something about the property, and know the area (slopes, kinds of properties), most of the time I can give them an estimate on the phone right then and there.
Whoever is answering your phone has got to be familiar with the area you work. Whether you are interested should be no mystery to the caller requiring a second call.