Make sure your add is the biggest add on the page. It is unlikely that the seeker will take the time to read every add on the page. You want them to notice yours first. If yours is done well enough, it may be the only one they see. Make it wide .
Movie screens are wider than they are tall.
This is because the eye is more comfortable viewing information that is wider than it is tall. Make your add at least two columns wide. Use color . As you browse the Yellow Pages you will notice that your eyes are drawn to the color ads first. Use a white background with blue ink.