I really feel that the whole PR issue is over-rated. Simply focus on doing the things that send traffic and real customers to your website. Its all about sales conversions and traffic.
Working on establishing inbound links from relevant sites should be the backbone of your niche's marketing. Of course it helps to have a site full of tons of quality content.

I focus more on SERP. But there are some niches in which having a high PR would be beneficial - directories, company sites, etc. PR is a gauge on how much links or ads can be sold in a site.

For PR - focus on building quality and targeted backlinks to authority, relevant and high PR sites.

Participating in DOFOLLOW blogs would also help ;)

I'm a small-sized business owner with what I believed to be a hot product and service opportunity. I was excited when I finally got my web page up to advertise what I had to offer. After a few months of very little traffic, I realized I was missing something. I enlisted the help of CastleWave who specializes in search engine optimization. Through their efforts and focusing on link building within my own site, my page rank quickly began to rise and I immediately noticed an increase in traffic, leading to an increase in sales. I learned that a web page is only a web page until you optimize it.

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Search Engine Optimization | Link Building | Web Traffic Monetization

get tons of inbound links! simple as that

I was able to get enough linkbacks in 1-2 months to get my pagerank up to 3.

Now, now matter what I do, i simply cannot get it to go higher :(. I guess i better keep adding!

Just remeber that quality outweighs quantity ;) Best of luck!