It's a good idea to make your site SEO friendly. I've copied and pasted some notes I took while reading a book on the subject below. (These were quick notes, so please forgive the poor grammar.)
Each page should have unique tags. No duplicates.
4 main ones: title, description, keywords, robots
Title: Title of your page in search results. No more than 7 words & less than 60 characters, including spaces (max for google). Include your keywords. The post "|" separates distinct phrases for Google.
Description: Description of your page. Use keywords twice if possible here (BING) but no more. Keep compelling and accurate as to what's on the page.
Keywords: Include main keywords, those that are main focus of website, and those associated with theme of webpage. Don't stuff too many. Separate with comma then space. Don't use words consequtively. ex. marketing, serach engine, marketing resources...
Robots: Happens every 2-3 days with Google. Set robot tag to "all" and they will crawl your whole site.
URL: Bing cares, Google doesn't much but it doesnt hurt.
W3C standards is big- validator.w3.org tells you if you're good.
<h> header tags are important, try to use keywords there. Try to use <h1> atleast once.
Images should all have alt tags. Don't overdo it with images though.
Keyword Density 2-3 %, but not as important anymore. Put keywords in title tag, description tag, keyword tag, alt tags, header tags, first 25 words of page, last 25 words of page, bold them at least once on the page, italicize or underline at least once.
Sitemap google.com/webmasters/tools. XML sitemap is advised. Include descriptions with keywords for each link. Upload to Google, it can help SERPs.
Internal Links Have navbar, don't link more than 3 times to same page on homepage. Include keywords if possible. Include links in footer.