Search engines such as Google, Yahoo and Bing use algorithms to rank sites based on such things as the number of links a site has coming into it, the value of those links, and how long the links have been in place.
The content on the site including the title, body content, menu links, and outbound links make up part of the on-page optimization. More of the onpage optimization can be found behind the scenes such as meta keywords, meta description, and the html & css structure of the site. All these parts need to be correct when doing proper SEO.
Link Building
As mentioned above under Search Engines, one of the most important parts of SEO is link building. Link Building can be difficult and if not done properly, you could be giving the search engines the wrong impression of your site.
more to come......