Tips to Increase PageRank:
PageRank (PR) is related to link popularity (i.e. other sites linking to yours), however it depends more on the quality of these links than merely the number. If you want to increase PageRank, concentrate on building link popularity.
Google PageRank depends on internal and external links. Look at its algorithim, and you can see both inbound and oubound links are taken. Thus, you may want to increase PageRank by enhancing the number of inbound and oubound links.
To increase the chance of getting healthy PageRanks for pages beneath the home page, make sure your site is linked together healthily. Link all secondary pages to the home page and to each other.
If you have several articles, in different directories on a similar subject, link these together too to increase PageRank - Google will see them as relevant and rank accordingly.
It is essential to exchange links with sites with a PageRank of 4 or more to increase your site's PageRank. Sites of all PR's are worthwhile and should be contacted, but those with 4+ will have a direct impact on your page ranking. If these sites have a subject relevant to your own, it will be even better.