i think it can probably be summed up this way:
1. Write and submit articles to the article directories.
2. Leave comments on other people’s blogs with a backlink to your site.
3. Answer people’s questions on Yahoo! Answers - Home.
4. Post in forums and have a link to your site in your signature.
5. Write a press release and submit it to PRWeb::The Online Visibility Company (this one's my own addition
but i have found it useful)