There is a lot of good information available on the internet, the following websites will help build your understanding of search engine optimisation.
http://www.idealware.org/articles/found_on_search_engines.php
A great article from Idealware – a leader in the NGO technology support field - which shows how “The content and structure of your website can have a dramatic effect on how easily potential constituents can find you via search engines.” Covers 10 steps that can help search engines find and prioritize your site content
http://www.idealware.org/articles/cms_for_seo.php
More information from Idealware on how to make sure the content management system used by your organisation to maintain your site is helping with your search engine optimisation.
http://seo.grassroots.org/guide
http://www.goodkeywords.com/
Good Keywords is a free Windows software for finding the perfect set of keywords for your web pages.
http://searchenginewatch.com/showPage.html?page=2167921
An in depth guide to search engine optimisation from one of the leading sites in this field
http://www.google.co.uk/webmasters/
This site offers inside knowledge on crawling and indexing issues and introduces offerings that can enhance and increase traffic to your site, and connect you with your visitors.