besides the PR toolbar, what tools do you find most helpful in quickly analyzing a site if you are going to place a link on? I am talking about cheap pr4-pr5 sites that you will probably be paying $50 for six months for?
I will generally avoid such sites because their cheap price will attract lot of spam and it will affect you as well. Best thing is to buy links in sites that have good editorial contents and strict rules about linking to quality sites only
The quantity and quality of external links. You can use the command linkfromdomain:site.com in Bing for checking.