It is the common understanding, a quality backlink that has a very big contribution to get a high PageRank. To get a backlink, there are 2 steps that are usually made of the blogger, is to exchange links and make comments on dofollow blogs.
To make a link exchange, ideally we do with a blog that has a higher PageRank, so that we get a backlink with a good quality. If we exchange links with blogs that have PageRank same or even smaller, less effect on the increase PageRank.
As well as comments on the blog dofollow. Moreover, now many blogs that dofollow logo, the commentary does not dofollow. To do this we must first check whether the blog is dofollow or not. Commented on the post that has dofollow PageRank is very difficult.
To know the quantity and quality of the backlink that we have, we need seo tool that can provide an explanation for the amount that we can backlink, dofollow or nofollow and have a PageRank or not. I recently found a link with the quality of the backlink information is complete. To try it, please visit this url: http://seopro.com.au/free-seo-tools/link-checker/.