You get a percentage of each sale, without risk or fulfillment hassles. Promote offline as well as online. Look for inexpensive ways to promote offline and online. Sponsorships with organizations in your subject area can be a handy way to promote your site. Trade banner ads on your site for ads in magazines or association publications.
Word of mouth is also a powerful promotion tool online.
Go to other sites in your niche and trade links or ask to get reviewed. The Internet is a world in swirling change. There's no success formula, but top sites that started small and carved a respectable place in cyberspace used these seven guidelines.