SEO Experts, of which there is a thriving business out there, will tell you how complicated Search Engine Optimisation is. However, there are a few basic rules which you can apply to any webpage/site. The list below give you 20 Ways To SEO And Promote Your Website...
1. Give each webpage a title which is relevant to the content of that page. Not the same page title for every page - as is often the mistake by those using a template mass production methods for webpages. Remember search engines, (and people's searches), will hit on any page in your website - they don't all come knocking on the front page asking to be let in :)
2. Use that page title in, at least, a main heading on the page using <h1> tags - which you can style using CSS to make them smaller :). Use <h2> and <h3> tags as well - usually once, or twice each. Again you can style these with CSS. But don't go over the top on <h> tags - it can go against you as well.
3. Use other keywords, (i.e. words a person would use to search to find your webpage), in the content/copy of your webpage. Remember - people who search with one or two keywords are really just browsing. People who search with a three, or four word phrase are usually looking to buy. Optimise for other phrases which may NOT be in the Google Adsense Top Paying Keyword lists, but ARE the phrases which REAL BUYING customers may use.
4. META TAGS - keywords, content, and description, can also be used. These are found inbetween the <head> and </head> tags in the HTML coding of a page. (Right click on any webpage and "View the source" for an example). These are not as important as points 1 - 3, but still hold quite strongly in the likes of Yahoo.
5. Viewing your competitor's actions, (for an e-commerce site), on points 1 - 4 can also help you to improve your own SEO, and ultimately your website's search engine rating, and ability to be found.
6. Appear natural in the search engines. (Not get 200 pages linking to you in 3 days).
7. Page length approx 200 words - 300 words max.
8. Easy navigation.
9. Site map (with text).
10. Relevant linking only to our site. (No reciprocal stuff)
11. New Content added every month or so.
12. Related articles (news).
13. Not to submit to search engines, instead let them find you through other sites linking to you.
14. PR releases. (Online as well as offline).
15. Links within the site linking inside the website.
16. Vary Anchor Text - the words used in text links out.
17. Bullet keywords, bold them, link them...
18. Keywords in <alt> tags for images - but NOT too spammy.
19. Get your website registered in like minded forums, webrings about your product/service.
20. Get yourself registered in forums such as Webmasterworld, or Webproworld - where you can talk about stuff like this - and put your website address in your profile, or your posting signature
And the other main thing to remember is that the changes you make to your website/page to improve your SEO - will NOT happen overnight. It make take weeks, or months, to see an improvement.
Hope that list is of some help to you.