The main factors for getting up the search engines are the textual content of your website, the links to and from your site and the popularity of your website.

Which is the most important is always changing as the search engines are always changing their algorithms. In fact it is believed that they change every day. The textual content on the site was believed to be the most important a few years back but now that is not the case as some search engine marketers were 'keyword stuffing', or putting certain terms on pages many times.

Now Google clearly state that links to your site are very important. Links from your site as well. How many people click your site in the search engine results is also important but it is clear to achieve all 3 well is important.

Your site's popularity is defined as how often the link is clicked in the results, how long people stay on the website and how many times they return.