Local telephone books are a less costly alternative to purchasing databases of
residents’ telephone numbers and addresses. If you use this method, be sure to
employ a randomizing strategy. An effective randomizing strategy is to take every
15th, 27th, and 40th line (for example) in the telephone book. You can measure
the space between the top of the page and the 15th, 27th and 40th line, and mark
these spaces on a ruler. Because these spaces will be consistent on each page, you
can then use the ruler to quickly go through each page and find the telephone
number or address for the resident on each of these lines.