http://www.seo2020.com/seo-articles/tag-and-ping.html
http://www.seo2020.com/seo-blog/12/tag-and-ping-review-of-sean-wus-e-book/
http://www.seo2020.com/seo-articles/social-bookmarking.html
http://www.seo2020.com/seo-articles/bookmarking-and-tagging.htmlThirteen Tips for Effective Tagging
How to mark sites so you and others can find them
http://www.techsoup.org/howto/articles/webbuilding/printpage4519.cfm
OPTIONAL:
By the tag and ping guide from SEO2020. It's only $25. If you don't have $25, don't worry about it, just make sure you study all his articles above.