People often believe or like to believe that the content inside the site determins what PR or PageRank the page gets. I should just clarify that Pagerank has nothing to do with content but the amount of backlinks it contains. Without backlinks there wouldn’t be a pagerank on that page. Internal links also count. Internal links meaning links from other pages on that site to that page and they do count.
Google webmasters can help you out by telling you all the different internal and external links pointing to your site and its page. If you pay attention enough, eventually you can start predicting if that page will get a PR next update or just go unnoticed. Of course the algo of the PR changes from time to time but again if you pay attention to how the algo is changing you can predit the PR of many sites and pages better than any script.