The higher the PR of your site the higher will be its search engine position. So the goal is to get lots of sites linking to your site. But quality is much more important than quantity. The higher the PR of the sites that link to yours the more they boost your sites PR.
When planning your effort, always remember than one link from a PR-6 or PR-7 site is worth indefinitely more than hundreds of links from PR-0 or PR-1 sites.
In addition, you should aim to include your link on pages with as few other links as possible. Pages with over 25 links have little value. Additional factors that go into the algorithm include the amount of different sites that point to yours (10 links from 10 different sites count much more than 10 links from the same site) and the inclusion of your keywords in the text of the links.
As a general rule of thumb, a one-way, high PageRank link will give your site a PR two points below that of the linking page. So a link from a PR-8 site should get your site a PR-6. However, at the lower end of the scale, I have seen a PR-5 turn a new PR-0 site into a PR-4.
The effects of having a high PageRank (PR)
Most industries, market niches and business sectors only have a PR5 or PR6 site as the top ranking result. The implication is that you can dominate a niche or local market on search engines without investing too much money or time. For example, you can buy keyword rich text links on networks of sites that have a PR of 8-9 for $ 500-2,000 a month. Doing this is likely to get you a PR of 6 or 7 right out the gate. The implication is that your site will appear as number one when users search Google for key phrases related to your market niche.
Where to start
Before starting to actually work on improving your PR, be sure to install the Google Toolbar on your browser. The Toolbar shows a value (on a log scale) of 0-10 for each website that corresponds to the underlying PR of that page. The average website with little or no marketing support is typically PR1 to PR3. Google is updating the PR level it displays in the Google Toolbar about once every three months so patience is required until you can see the results of any PR building campaign.
Since PR is all about links you