Actually, Page Rank and Keyword placement are 2 separate issues.

Your keyword placement isn't dependant upon page rank one iota.  Your page rank simply determines other people's page rank when you link to them.  You could be #1 for greed and have a page rank of 3.  If you don't believe me, type in greed in Google and go to the #1 site (which is currently http://hem.passagen.se/mada8981/).  Guess what, they have a PR of 4.

Keyword placement is determined by a whole bunch of different things like how well you designed your pages, how much you repeat key terms, etc.  You will be much better off focusing on how to optimize your site for keyword placement than worrying about PR, since people don't search Google for PR, but they do using terms.

This is just my opinion.  I'm certain someone else can find reasons why I am wrong.

To answer your second question, to improve in PR, if you still want to do that, you would need links from higher ranking sites at a basic level.  I don't understand the complexities of the PR formula, so I can't say what else would do it, but the number of people who visit your site wouldn't affect PR since Google doesn't track page view/visit statistics.

Hope this helps.