There are two types of Ranking: Page Rank and SERP ranking. Both of them depends on the link building factor. In order to get good rankings in SERPs, you will have to work hard on building quality backlinks. Quality backlinks are those which are built through high PR, high Authority and Relevant sites. An effective type of link is an In-content link, which is valued more by Google. Building quality backlinks will boost your site for targeted keywords as well as helps you to get a good PR for your site. PR depends on many more factors such as a site updated regularly with unique and fresh content, neighborhood of site, structure of site, design and theme of site, etc...