I have already posted a post with some SEO optimization tips. Let's continue this topic.
1. Try to put your keywords and key phrases closer to the beginning (top) of the page.
2. Use sitemap.xml to give search engines more information about the structure of your web site and pages.
3. Use mod_rewrite to build user-friendly URLs. www.yourdomain.com/cars/toyota/corolla looks better much than www.yourdomain.com/index.php?cat=cars&make=toyota&model=corolla.
4. It's not easy to succeed in SEO optimization just for one single keyword, therefore focus on key phrases.
5. Make sure you have properly set up robots.txt.
6. Name images on your pages accordingly to the page context.
7. It's good to host your web site on a dedicated IP address.
8. Use HTTP header “301 Moved Permanently ” for redirects if page has been moved.
9. Make sure that your pages that has important content are accessible at least in 2 clicks.
10. Avoid Flash clips if it is possible.
11. Avoid using frames.
12. Do not cheat! Don't lie to search engines!