What coping mechanisms did you use to deal with difficult or angry callers at your job?

In my job, I get many calls. Some are from people who are experiencing distress or anger, and they are often agitated.

I would like to know how you handled these types of people in your life? Did you experience the difficulties on the phone, or did you deal with these issues with people face-to-face?

What skills worked to help you maintain your cool demeanor?