Do a search on Google for "Google Page Rank Checker". That will give you several links to sites where you can see if a domain name has a page rank or not. The Google toolbar will also tell you if a domain has a page rank when you view that domain in your browser.
The exact methods Google uses to determine page rank are not disclosed by google, although another search can give you a pretty good idea of how to build up your website's page rank. The easiest way is to get other websites to link to your site. If a PRX domain links to your site, google will eventually find your site and hopefully give it a page rank as well. There are several other methods, do a search and you'll be able to find lots of information.
Hope this helps.
-Nitro