Most people get backlinks to their sites without even considering some important facts about backlinks. But, before getting those links, consider these points:

The relevance of these links to your site is very important. The webpage containing your link should be relevant to yours and/or mention your keyword in it's content. This will help generate traffic and determine your link popularity.

Your keyword should be contained in the anchor text of some of the links to your site. This will help you rank high for your keyword.

Your link building velocity is very important, because Search Engines like Google considers closely the speed at which a site acquires links. So, get backlinks at a slow and consitent rate to avoid suspicion.

Always bear these in mind while getting those links. Of course, go for links from sites with high Page ranking. This is link quality. All these put together determines your link popularity - hence giving you a high PR. Other points are highly welcomed...