I would identify an audience by finding out if it was a single person, like reader of my novel, or a group of selective people, or just a generalization. I also have to know who I want to target. If I want a group of republicans on my side, I would favor the republican view, and vice versa.
Website here. The target audience is anybody that is interested in what is going on and what they can do to help kids in foster care. They have a mission statement, campaigns, and a donation center. The main page gives information on current statistics and problems in foster care. All of this is directed to an audience that is looking to help or just learn more about it in general.