First, read the following article:

http://www.perfect-optimization.com/

Make sure you use the free tools they offer to analyse your website and make corrections in your website accordingly.

Next, go to:

http://www.seo-writer.com/reprint/top-seo-tips.html

This article presumes knowledge of certain SEO methods so if you feel at sea, read the series of articles on SEO that you see at the bottom of the sidebar. The following is a good place to start:

http://www.seo-writer.com/reprint/seo-basics.html

Once you’re comfortable with SEO terms and techniques, try the following:

http://www.seomix.com/

Once you’ve learned and begun to apply SEO tactics to bring visitors to your website, you need to optimise your website convert visitors into buyers. Therefore, BEFORE you actually apply SEO tactics vigorously, you may want to read the following article:

http://www.powerhomebiz.com/072005/conversion.htm

The following article also has some good advice on selling online:

http://www.ebizwebpages.com/how_to_sell_online

All the best