There are a number of factors, both on-site and off-site which affect how SERP rankings are assigned. The on-site includes the design of the website, title tags, links within the site and content on the page.
The off-site involves building the sites domain authority and establishing credibility through backlinks from external sites, citations, social media, online directories, blogs, reviews and unaffiliated sources.
Search Engine and SEO
The Search Engines algorithms are updated constantly, always seeking ways to improve the search results and help users find what they are looking for, both quickly and easily. Algorithm refinements affect websites in different ways, making SEO a continual process of anticipation, and adjusting and refining; however the concept remaining the same.