I agree with 'silveraden' he is right, no one really knows how google rank your site. I have experience with 2 sites. Both sites PR is same '3'. one of the sites have 1000 of backlinks, above 500 content page and monthly above 10000 visitors. On the other hand other site PR is same '3' monthly visitors only 100, baklinks 100 and more than 100 content page. So, how can you judge PR?:) so it is difficult to find how Google give PR to a site. So, it would be better if you keep all the aspects of SEO in mind, it will natuarally gain PR from google.
take care all the on-page SEO factor like
1.HTML & CSS coding should be clean.
2.Proper site navigation.
3.Proper Meta detail
4.'alt' tag on the image code
4.404 error page create
5.Internal link building
6.add social share button etc.......
7.update your site content weekly or daily
To get the PR you just have quality content, because backlink could only be counted if the content is relevant. And the quality of backlink is essential to increase PR, and please create them naturally.