the quickest way is posting in forums, blogs and submitting articles. there are other ways you can get more quality links but gaining links from relevant high PR websites can in turn raise your website PR
The best way to promote a website is considered to be one product of any another product offline. That means, much work in the introduction to the market and to maintain and increase their levels of exposure. Blogs, directories, forums - are all good tools so that you know. Each of them it works differently.
Do forum posting, blog commenting on do follow sites which has higher page rank and related to your niche and use social bookmarking and social networking sites to promote your website too.