What is the best way to pacify an irate customer?

It's very important to remember that the customer coming to us with a complaint or concern means most likely that customer care about our business. Probably 9 out 10 customers will not even bother to give us that opportunity. And highly like will not come back again. So, first and far most, it's important to believe and listen to customer's complaint or concern. That will make customer feel valued and comfortable. Then an apology is must followed by a satisfactory solution. Last but not least thanking customer will make them confident to come back to us and contributing towards our business.

First, get a room to isolate the customer from all the others. This is to avoid drawing attention from everyone else nearby. Politely invite him/her to a room where he/she can be comfortable. A comfortable environment would ease up the tension. Then, hear his/her out. Let the customer speak about his/her experiences and frustrations to your service/product. Don't forget to look at the customer in the eyes and take down notes to make her/him feel that you are really listening. After the customer finished the talking, offer her some refreshment, this is to calm him/her so that when it is your turn to talk, it would be easy to explain things.

Always begin your conversation with an apology. No matter whose fault it is, an apology is the best way to lower any tension. Then discuss recap the complaints of the customer as if asking for confirmation that you have the correct understanding of the complaints. After the confirmation, lay down the reasons why such things happen, explore the possibilities and come up with a solution. 

Then ask for the customer's opinion and discuss a win-win solution that will not compromise both the customer and the company. 

It is important not to leave the room without an assurance that the customer is satisfied with your discussion.