Important factors of PageRank:
This is one of many secrets of Google that how Google give you pagerank but I have guessed some of these secrets and factors.
(1) Domain (URL) Age
Domain age is an important thing that Google consider when it gives you page rank but this is not all, it is just one thing. And old URL will have higher page rank than new if everything is same except age, so calculate how old your site is.
(2) Website Category
It is very important factor that Google consider in page ranking. Blogs are filled in blog category. So any blog would not have more than PR8, blogs also has categories as Tech blogs, personal blogs, humor blogs, gadget blogs etc. Technology blogs have higher pagerank. Find out in which category your website is filled.
(3) Content (of website) quality
If your website is a blog then content quality is most important than any other factor. Your blog should be having quality content. Check out the quality of contents.
(4) Content Quantity
It is also very important that Google consider for a websites page rank. A pagerank is just of the page you are viewing but page rank of homepage is overall page rank of your website because people consider page rank of main URL not entire posts or pages. A blog has only 500 articles and other blog has 5000 articles in this situation the other blog will have higher page rank than first one.
(5) Content usability
This factor can never be ignored, how important is your content for readers and what kind of content your write? If you write about web standards or an open source program you will have higher pagerank no matter if it has only some documentation pages and a download link.
(6) Content (Website) Accessibility
This is for web standards, how accessible is your website. It contains website navigation, technology you have used to design your website etc, is there any support for blind people?
(7) Website Traffic
If a website is getting high traffic normally it will have more than PR4.
(8) Backlink and Quality of Backlinks
This factor is measure of overall calculation. This is very common factor most of webmasters know about, it is important for both page rank and search engine ranking. If you have backlinks in good quantity this will help you and if you have backlinks from higher PR sites then sure you will have good page rank.
How you get pagerank first time?
When you register a blog and start blogging, for a few days it does not have any page rank but after a week it gets page rank of zero (0). After creating your blog if you post regular on good topics and your blog gets some visits you will have a page rank of 1 to 4. It depends on how much and how nicely you have worked on it.
If you keep continue your work and improve your sites performance and everything is fine you will increase your page rank again. But a website can have maximum PR10 and blogs never reach PR9. If you are really a good blogger you can gain PR6. PR7 or PR8 is normally for top and multi author blogs.