I thought that I would put my two cents in with the "quality over quantity" which seems to take on many forms depending on who you are talking with, however, with the attribute of increasing
PR, the best method is to get links from pages (actual
PR pages) from higher
PR than yours, i.e. if you want to go to
PR 6 then find a good
PR 8 link with minimal outbound links. I have tried it myself, and one
PR 8 link will give you a
PR 6, furthermore, if you are building from a variety of other places to increase serps you may even get lucky and have a
PR 7. Now a high
PR doesn't mean you are going to rank well in the serps, based on data the search engines take impressions into consideration so the site that is
PR 6 from the
PR 8 link will very little impressions and will not show up in the serps, therefore you have to have a combination of high
PR links, and impression links with your anchor text keyword to get the best effect, while consistently adding pages to your site with great content.