The PageRank feature on the Google toolbar lets you know how important Google considers the page to be. When installed, the Google toolbar will show you the rank of every page you visit. Many experts consider the PageRank to be the most important factor in establishing the relevance of your web page for each particular search phrase typed into the Google search box.
competitive search terms, you should concentrate on on-page optimization.
If you still don’t achieve higher positions, then try to boost the PageRank to 4 or 5. PageRank 4 and 5 are seen as fairly relevant sites and unless you are in a really competitive market, it is probably sufficient to rank well if the on-page optimization is in place. PageRank 6 or higher is sufficient for almost any area of the market.
If your site has PR6 or above, other webmasters will naturally want to link to you, so you will be offered reciprocal links almost every day, allowing you to further strengthen your PageRank with little effort.