According to Google:

PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page‚Äôs value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves “important” weigh more heavily and help to make other pages “important.”> Important, high-quality sites receive a higher PageRank, which Google remembers each time it conducts a search. Of course, important pages mean nothing to you if they don‚Äôt match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search. Google goes far beyond the number of times a term appears on a page and examines all aspects of the page‚Äôs content (and the content of the pages linking to it) to determine if it‚Äôs a good match for your query.
I wish there was a quick and easy way to do this but there isn’t. As stated before, Google is a democratic search engine. Using the strategies outlined in the previous articles you will slowly build your pagerank. Ultimately, each page that links to you should have a higher page rank then you. The higher the page rank on the pages that link to you; the higher your page rank becomes.

Also, remember that each page a person links to on your site should target a specific keyword. The links from the outside sites should link to your page using the targeted keyword. In the end, page rank is a function of how long you spend using the tactics previously mentioned.