There are many variables to out ranking the competition in the Search Engine Optimization (SEO) process. The most fundamental elements are as follows:

a) Keyword selection that accurately represents your marketing objectives.
b) Keyword ranking difficulty, ie. how competitive is the keyword?
c) Well written content that supports keyword themes.
d) Proper on-page optimization.
e) Internal linking strategy, ie. how your menus and page links are formed and organized for accessing the content of your website.
f) External linking strategy, relevant inbound links or link exchanges with other sites.

The more competitive the keywords are, the proportionately greater amount of content and inbound links that will be required. This is a significant factor in cost of SEO.