Rule One: Stick to Your Keywords
Pick a few keywords or phrases that describe your site. Use them, and words related to them, whenever it’s natural to do so. Repeating them uselessly is no good (rule Zero), use them in sentences, headlines, and links.
Rule Two: Content is King
Users don’t search for design, they search for content. If your site doesn’t have content people want, no one will look at it.
Every page on your site should follow the Inverted Pyramid. Each page should lead with a relevant H1 tag with one of your keywords, and the first paragraph of text should be a summary of the rest of the page.
Rule Three: Clean Code is Searchable Code
Build your sites in a text editor, and write clean, human-readable HTML. The HTML should follow the conceptual structure of the page, navigation first, followed by the H1 tag, then the first paragraph, etc. Try to use descriptive tags when possible. Use UL for lists, P for paragraphs, H tags for heads and subheads, and STRONG for bolded text. Don’t overuse Divs.
Your site can still be artistic and cool, that’s what CSS is for.