Title:
A good title has between 10 and 70 characters (including spaces), and contains your primary keywords and phrases. Be sure that each page has a unique title.
http://blog.magnoliasoft.net/2009/01/title-tag-best-practices-10-step-guide.html
Meta Descriptions:
The Meta Description Tag doesn’t affect your page’s ranking in the search engines (for the most part), but it is still important for your SEO. Google may choose to display meta descriptions in the search results, this will help users to have a clear idea of the URL’s content. Its worth to have a accurate meta descriptions, and this may improve your Click-through. Try to limit its length to 60 – 150 characters.
http://googlewebmastercentral.blogspot.com/2007/09/improve-snippets-with-meta-description.html
http://en.wikipedia.org/wiki/Meta_element#The_description_attribute
Meta Keywords:
Although the keyword meta tags don’t count in Google’s ranking, but it is still a major factor for other search engines consider.Ideally, your meta keywords should contain no more than 256 characters, and separate the words or phrases using a comma.
Headings:
Heading tags help search engines to recognize which are “important” on your web page. Include your main keywords in the headings, and make sure use one <H1> title per page.
Scripts:
Use Google AJAX Libraries API has several advantages over hosting open source Javascript Libraries on your server: decreased latency, increased parallelism, and better caching.
Bold Tag:
Put your keywords into italics, bold, or emphasis (<em>) to make sure the search engines know that these words are important.
Italic Tag:
Put your keywords into italics, bold, or emphasis (<em>) to make sure the search engines know that these words are important.
Images:
Add alternative text (the alt attribute) is helping search engines to better understand the content of your images. Limited number of images to optimize your page load times.
http://www.seosmarty.com/image-seo/
Text/HTML Ratio:
A Text to HTML ratio of below 30% is not favorable for SEO. Including more relevant text to your pages and increasing your keyword density.
Frames:
Frames can cause problems for search engines because they don’t correspond to the conceptual model of the web. It is advisable to minimize the usage of frames, whenever possible.
Flash:
You can use flash as some specific enhancements, but it’s better to avoid a full Flash
websites to maximize SEO. However this may change in the near future.
Site speed is an important factor to search engine optimization (SEO). Using free tools like Page Speed to evaluate and improve your website speed.
Gzip is a form of content compression and helps speed up the loading time of a site. It is advisable to use this for large website with lots of contents.
XML Sitemaps lists the URLs for a site. You can include additional information such as the frequency of changes and when the last update was. This allows search engines to crawl the site more intelligently. You can use GoogleSitemap Generator to generate an XML sitemap for your website.
Robots.txt:
A robots.txt is regular text file, you can instruct robots to not crawl and index certain files, directories within your site, or at all. Click here to check your robots.txt file for syntax errors.
Broken Links:
Broken links are links that lead nowhere. It may adversely affect your website search engine rankings. Poor usability from broken links can drive your potential customers away and prevent search engines from properly indexing your site. The usage of a customized 404 error page is encouraged.
Indexed pages:
These are the number of pages that are indexed by each search engine. You can use Google webmaster tool to submit a sitemap or ping service in order to speed up the indexing process.
Backlinks:
Backlinks or Inbound links are incoming links to a website or web page. This is a crucial factor in search engine optimization (SEO), as this is an indication of how popularity or importance a website is.
http://www.seomoz.org/article/search-ranking-factors
http://www.seounique.com/blog/anchor-text-optimization/
DMOZ:
DMOZ is a multilingual open content directory of World Wide Web links. Submitting your website to DMOZ has a positive effect on your SEO.
