The main 4 factors of Search Engine Marketing SEM) are as follows

Keyword rich text. The majority of a site's pages should contain the words and phrases the target audience types into search queries. Pages should appear somewhat focused on these important keywords and phrases, and the phrases should be featured prominently on the page, title, keywords and description. Otherwise, the page won't convert well or receive consistent search engine traffic. Keyword research and copywriting for individual HTML tags are a part of this effort

Information & page layout. Search engines and end users must be given easy access to keyword-rich content. How text is arranged on a page tells search engines and site visitors which content the site owner believes is most important. URL structure and technical architecture figure into that as well.

Link development. Commonly referred to as link popularity, this is the number and quality of objective, third-party links pointing to a URL or Web site. Of course, not all links pointing to a site are objective, having several link backs to your site from external sites and pages are very important for your showing up among the first few results on search engines.

Contextual Advertising. Even with all the SEO efforts you may not get enough traffic to your site. It is advisable to do some targeted advertisements on Google and Yahoo in order to get additional traffic. Since Google's adsense and Yahoo's publisher networks places text ads on millions of third party webpages your reach is vast when you are part of such a network. The SEO only works to your favor only when visitors are searching specifically on the search engines site. Contextual ad placing Google and yahoo are doing will be a very valuable area of traffic building you may want to explore.