If you are in business (especially sales), you will eventually encounter a customer with a very difficult personality (if you haven't already). It may be that they are having a bad day,going through a difficult life or career experience, or maybe you just rub them the wrong way. Whatever the case is, in order to be successful in business we have to learn how to handle these types of clients. Here are a couple of things that I have employed that have helped me:
Keep calm- Your calmness has great power to diffuse the most hostile of clients. This may even put them at ease, because calmness conveys confidence and control. These are traits that your customers want to see in you (even if they don't know it).
Give ear to their frustration- If the customer isn't cursing at you or belittling you (to a point that is unacceptable), just listen to them and try to discover the heart of why they are upset. People want to be heard and many times they will come to their own solutions by talking it out. This will also help position you to serve them better. Conflict, if handled right, can create a bond between two people that sugarcoating can never produce.
Show empathy- acknowledge and validate their feelings even if you don't agree with their viewpoint. In this way, you show respect and raise the level of your conversation, not to mention, it shows that you can take a punch which is a huge testament to your professional caliber.