I have said this before many times. That page rank is not as important as many webmasters think it is. Google now admits it openly. Source. In fact, they are going to rename it according to that article and they do encourage webmasters and SEO not to put page rank as their main goal of SEO.
And I couldn’t agree with this more. While I think link building remains to be THE MOST IMPORTANT THING in SEO, but one should not expect links to increase his PR and if it does, that doesn’t mean much anyway.
In my opinion, a good SEO strategy is to get as many links you can from diverse sources both relevant and non relevant. Relevant sources mean websites that have contents relevant to yours. Also good SEOs go beyond traditional SEO techniques and work on link baiting, coming up with fun and unique ideas to get users to come and visit their websites and link to them.
I will have a well put post in near future about link building but remember, PR is not longer the factor on link building.