The best indicator of future behavior is past behavior, which is why interviewers want to know how you handled situations in the past. It is important to provide detailed examples of how you dealt with stressful situations, irate customers, and poor employees. They also want to know how you handled projects, with descriptions of the steps taken, mistakes made, solutions found.
It is hard to provide examples to assist you with this without knowing something about the position in questions or about your previous positions. But I can tell you this: don’t say, “I just try to calm down a customer who is irate.” That answer is not detailed enough. You must explain why the customer was irate and exactly what you did or what you said to calm him or her down. Provide detail so that the interviewer can get a good picture of the situation. That said; don’t go on for 10 minutes.