1. Relevancy
Is the website or page relevant to your business style? For example, if I have a website that sells computer software, I want to get links on software related sites. It does not have to necessarily be a competitor but could be a site that reviews different software, products or covers news related to software.
2. Indexed By Google
One of the most significant factors to look at when securing a link on any specific web page is whether that page is basically indexed by Google. Common sense would tell you that if the page is not in Google’s index, they are not going to identify that it is linking to your page. In other words, the link wont count in their eyes.
3. PageRank
While Google PageRank is definitely not everything, a PR 5 is certainly better than a PR 1. And a PR 7 or better has the prospective of passing a lot of link juice to the page your linking to. That being said, I would recommend having a good mix of links from different PageRanks as it looks more organic.