Keyword Densityis of utmost importance for a defined SEO Status. Too much and your page is listed for spamming, and too less, it does not get the ideal SEO standing.
Quality Backlinks is another factor that augments SEO Status. A modulated number of backlinks that co-ordinate keyphrases with your website , will automatically upraise the SEO of your content.
It is essential that any redirects set up by you, on your website is easily crawled by the Search Engine. Suppose you have a website http://www.foo.com and you create a redirect such that whenever any visitor types in the URL http://www.foo.com he is automatically redirected to http://www.foo.com/widgets/, If the Search Engine is not able to follow the redirect it would think that http://www.foo.com has NO contents, http://www.foo.com would end up ranking very badly in search engines.
Reciprocal links, specifically 2-way/3 way reciprocal link exchanges are popularly recommended for getting backlinks for your website.
Optimizing content by manually submitting in Web directories and specialized search engines is a must if you are looking for quality visitors, and those with a particular interest in the field concerned. Once you do this, you automatically get noticed by Google crawlers, which enhances your link popularity.
Often, as the case maybe, you want to omit some web pages from being indexed, like JavaScript, and Images. Robots.txt is a text (not html) file you put on your site to tell search robots which pages you would like them not to visit.
Unless you place the robot.txt in the main directory (otherwise search engines do not find it), the effort goes in vain, and search engines crawl all your pages.
Sitemaps, which are 1 page structure of your sites, are beneficial for both search engines and users who want to navigate your website. Google Sitemaps uses a special (XML) format that is different from the ordinary html sitemap for human visitors. Ideally, you need 2 sitemaps one in html format, and the other in XML, and this is not considered as duplicate content. Any changes in your websites are indexed faster once you have a sitemap, than otherwise.