Sorry for ressurecting an old post, but along the lines of what kzhivago said, you might place a door hanger on the door handle if people aren't home when you go door to door. This is basically a small flyer, roughly the size of a #10 envelope, with a hole in it to fit over the handle. They're pretty cheap. This would likely be most effective once you have a few clients and you can advertise in this way to their neighbors. If they can see an example of your work from their doorstep while they are holding your advertisement, or walk over to the neighbor's house for a quick reference, it will give you a big edge over the competition.