It's a lot like writing a good classified ad headline. Your goal is to catch the readers attention and get them to click on your link to learn more about your offer. Don't try to say to much in your ad. By the way, I doubled my daily visitors within less than two weeks doing daily FFA page promotion. Your results will of course vary, but if you offer something free or interesting you will probably get a very nice traffic boost.
Free items work the best.
Use a free report, sample, or demo of your product or service to pull people into your site. If you don't have a free offer, then search around for one that you can use. The Internet is full of freebies that you can give away or reprint. To get the best results, you should submit your most important URLs to as many FFA pages as possible. Submit once each day or once a week if you do not have the time to do daily submissions.