Customers can have a nasty attitude for no reason, either way, what techniques do you employ to calm down customers when they are irratated?

just listen to what he/or she says...do not interrupt and let him/her burst his/her feelings.  And after that, that's the time you approach your customer politely and ask what the problem are. Try to be calm and never get intimidated or irritated with the customers about their behaviour.  Try to understand him/her, of course there's always a reason behind. Show empathy and sincerity that you are willing to give help as much as you can.

Attitude is everything in creating satisfied customers. Even the most irate customer will usually calm down when dealing with someone who is obviously doing their best to understand the customer’s situation. If employees truly listen to a customer complaint, valid or not, the customer will at least feel as if they are being heard. Sometimes that’s enough to completely diffuse a negative situation.

In my experience most clients do not understand that there are a lot of things that are not in your control. or power.For example, when they are complayining of their bill or service and you are not involved with the way sistem works or how they talk on the phone. They damand to be refunded and they yealed at your face. Other times they just had a tough day or are nervous. You have to be calm, explain kindly and move on. 

When customers are irritated you should:1-Listen to them (to understand their problem),2- Do not argue with them again if they are wrong,3- Inform them that you are trying to solve their poblem,4- Take action towards solving the problem

Agree with Venera Sokolova ...Good answer.

Good question for a sales person, you are right most of the time attitude of customer irritate & hurt. but be bold and smart to know that you have the product knowledge of your assignment and customer dont have that so its your duty to explain this effectively. another thing which is to be noted that most of the time customer dont realise the real need of your product so establish the real need to him. you have to convert innitial NO of customer into YES, it may take time but be consistent and have passion , you will do it because you do it, that is reason you are in sales. good luck

Listening to Angry Customers could be the First Magical Tool to Earn them Back

2nd step would be Understanding the whole Problem or whatever Bother them