1) Title Tag - The title tag is the most powerful on-site SEO technique you have, so use it creatively! What you place in the title tag should only be one thing, the exact keyword you used for the web page that you are trying to optimize. Every single web page should have it's own title tag.
2) ALT Tags - ALT tags were meant to be for text browsers because the images didn't show in text browsers and the ATL tags would tell the visitor what it's about. You should put your main keyword(s) in the ALT tags, but don't over do it because you could get dropped in the results or even worse banned for life!
3) Link Popularity - Link popularity is the most powerful SEO tool out of all them. Most search engines don't even consider web sites if there is not at least one or two links pointing to the web site. Having another site(s) link to your web site is important when it comes to getting your site a good ranking. Your keywords should be in the links you get and keep the keywords short. When you receive requests for a link exchange, check the site out before linking with them, check for spam (Repeat keywords, hidden text, etc.).
4) Keyword Density - This is also vital and should be used with research. You should use the keyword(s) once in the title tag, once in the heading tag, once in bold text, and get the density between 5% to 20% (Don't over do it!). Also use your keyword(s) both low and high on the web page, keyword(s) should be in the first sentence and in the last one.
5) Page Size - Your web page's speed is important to your visitors and the search engines. Why? Because the robots will be able to spider your web page faster and easier. Try your best to keep your web page over 5k and under 15k in size.
6) Rich Theme - Search engines are looking at themes more and more. Build content (Articles, FAQ, tips, etc.) much as possible and keep the web pages around 200 to 500 words. Create content that's related to your market and link them out to other related content on your site. Try to get 200 web pages or more.
7) Web Site Design - This is also important, if you want to get indexed! Text content should out weigh the HTML content. The pages should validate and be usable in all of today's leading edge browsers. Stay away from flash and Java Script, search engines dislike them both a lot.
8) Insite Cross Linking - This will help you get all of your web pages indexed by the search engines. Your web pages should be no more than three clicks away from the home page. Link to topic related quality content across your site. This will also help build you a better theme through out your web site. On every page you should link back to your home page and your main service(s).