Crisis communications is a very important aspect of public relations. Even thought they are unwanted, bad things do happen to people. Crisis communications is a way to prevent crises, or in the case that they do happen, help do damage control. It is imperative that the public relations specialist knows who the audience/publics are and the most effective way to reach out to them.
There are seven cardinal rules in crisis communication: To accept and involve the public as a real power, plan carefully and use evaluations to judge your efforts, listen to your public’s questions, concerns, and comments, be honest and open with your audience, collaborate with other sources that can strengthen your organization, cooperate with the media, and speak clearly and with compassion.
http://www.globalprblogweek.com/archives/basic_principles
http://www.levick.com/resources/topics/crisis