I dont know for sure, but my web use to be pr 6, and recently drop down to 4 due changing the main access to the web to a login page, so i guess having a good pr also depends on the updates you make to that main page not only content or links
You need to do a few General things to increase page rank. 1. You need good content and content that is optimized with unique titles, descriptions, alt tags and header tags. The more pages your site has the better. 2. Build good back links. A bunch of PR 0 sites linking to you will not help very much. Also, Google likes sites that have links pointing to internal pages. If all your links point to the home page, Google considers them unnatural and could penalize you for it. Along with this there are certain links that Google does not count for one reason or the other. Having a bunch of directory links may seem great but the fact is that Google ignores many directory links and those that it accepts are often accepted with a heavy penalty attached. 3. Make sure you aren't bleeding page rank by linking to too many sites or places. Use nofollow attribute whenever possible on unimportant pages like contact forms that would have little real content. 4. Make sure there isn't a major problem with your sites architecture. Recently I worked on a site that had been PR2 forever. I fixed its navigation structure and a few coding problems and the last Google update the sites PR doubled.
Submit content regulary, submit to directories, add your link in forum signature, post on blogs with your link etc. There are a lot of ways for doing it.
Try to keep the contents fresh, build up back links,try hard to generate good traffic than wait for a good time.