Important factor of off-site search engine optimization is an external linking
This process improved the ranking in search engines and also improves page ranking (from 0 – 10).
How the external linking works?
To create external link, you need to submit an article, directory entry or any entry to a website not hosted to your server. It has to contain clickable link pointing to your website.
How is the page rank calculated?
There is not specified rule by search engines. In general experience of SEO specialists it appears that 8 links of certain level are required to reach next one. In practise it means that you need to have 8 pages with page rank 1 pointing to your website in order to reach page rank 2.