There appears to be no definite guidelines or goals on how to build backlinks and increasing your PR but their results are the same on whatever guide or pattern you make, you gain more traffic and that affects your PR.
There are 3 key methods among the several methods that I am currently applying on my sites to increase the traffic and PR.
1. I recently joined digital point to gain more knowledge on SEO and how to run an effective forum. This is one informative forum on SEO, and at the same time it encourages you to post, you can add signatures on your profile after 7 days of being a member and have atleast 10 post. 4 signatures can be added which is a rich method of backlinking to your website. The more post you generate the better the backlinks to your website.
2. If you are running a blog, you see spam comments on your post all the time which are generic post or generated by bots. Concept is commenting on blogs allows backlinking, so try to converse with the poster when you comment to generate a discussion instead of just appearing spamming the post for backlinks. Comment on blogs with the same niche as yours or with high PR can bring you not only traffic but also high PR.
3. The other method you can try to increase your PR is submitting to link directories, there are 3 types, paid submission, reciprocal link and free submission. Some link directories have a higher PR. Do not link to link farms for this could lessen your PR instead of helping.