Just like classified ads online these are a way to post a short ad that is meant to get a response and make the reader go to your site or email you.
But unlike their online counterparts, offline classifieds work much better. Where online you might get a few prospects but hundreds of SPAM messages, offline classified ads will consistently bring in prospects which you can turn into customers on your site.
Follow the same rules we have already been over for writing ads. Follow the same rules for your market and carefully target who you are going after. Take the same list you may have of publications you could write articles for and place classified ads in them.
The cost is much higher for traditional classifieds, but as I said before the return on investment is much better than the poor online variety.