Page Rank is a qualitative value between 1 to 10 which is assigned by Google to a web site or web page. 1 represents the lowest end of the scale and 10 represents the highest. The higher the number which Google assigns to a site, the more useful and supported (popular) that site is deemed to be and consequently, it will be more visible in search engine results.
Increasing Page Rank is obviously a goal for most sites. The Page Rank value is calculated by the Google algorithm, and so by taking note of what this automatic process is designed to respond positively and negatively to it is quite straightforward to boost a ranking.
It is important to avoid using tricks and short cuts to artificially push the Page Rank higher. The Google algorithm is frequently updated and particular care is given to devalue sites which employ tactics which are seen to be dishonest or attempt to manipulate the process. Without this, safeguard Page Rank would have no relevance.
It’s a good idea to look over the official Google site and keep up to date with new rules and warnings. If your site involves a practice which Google disapproves, then your ranking may be negatively affected. An example of one such practice is having sections of keyword text on your site in the same color as the background, rendering the words an invisible keyword spam. This is a practice which can be picked up by the algorithm and may result in a lower Page Rank.
A legitimate way to move up the rankings is back linking or acquiring links from other sites. Each link to a site undergoes an evaluation by the algorithm. Being linked by a site with a Page Rank of 10 will have a more positive effect than a link from a site with a lower ranking.
It is not advisable to set out to merely acquire as many links as possible. In fact, links from sites which have been blacklisted in some way can actually damage a Page Rank. Seeking out and cultivating high quality links is the best way forward. Instead of getting reams of random back links from obscure sites, it is better to seek out a handful of good, relevant links.
Aside from back linking, the perceived value of the content on a site is also judged by the algorithm. If a site does not have the positive features which the algorithm is looking for, then the site will not rank as highly as it could. For example, Google prefers large sites with regularly updated content and accurate keyword descriptions.
A high Page Rank is a positive thing to have but it is only one aspect of search engine optimization and creating and running a successful website in general. It is important to see all the different methods of improvement, ranking in balance, and working together rather than overdoing one aspect and neglecting another.