Page Rank is a convoluted subject in the Seo world and most do not know how to apply actual PR to their site. First of all, if you get a link from a site you have to look at the page. That is why it is called page rank. If is zero, then the link you get is zero, which is the truth. I don't care if you go to delicious and get a link, the link is zero. Now how to increase page rank; get links from higher pr sites than yours and they have to link back without the nofollow attribute, or you will not get the PR juice back to your site. You have two options, get a bunch or thousands of PR zero's or get a few PR 6's back to you site, that is the difference between link building, and quality link building.