1. Don't say, "I know how you feel." The first reaction is always "No you don't." We all believe our experiences are as personal and unique as we are. You should empathize, not sympathize. You can say things like "That would really be frustrating," "You might be right about that," and "I can see this is very important to you."
2. Listen carefully. Often you'll get tipped off to the real problem. Reflect back some neutral words and ask for a confirmation such as "You're concerned you were overcharged, is that right?"
3. Look for choices. Giving the customer a few choices is a great way to give them a feeling of control over the situation. Often when people are angry it's because they feel helpless. Give them what they need.

Secondly, let's look in the mirror. Did your company make a mistake? If so, the first thing you need to do is apologize that a mistake happened, and then figure out how to make it right. If they ordered their widget in red and it comes back blue, maybe they can live with blue with a discount. If not, get the red one and eat the premium shipping to get it overnighted. It's also important not to blame other areas of your company. Avoid saying things like "Whoo, yeah, they always screw it up. I'm surprised it's not as bad as some I've seen." This is very damaging for your company as a whole. You want the customer to come back, and you want them to recommend your business to their friends.

However, if you've done nothing wrong and it was a miscommunication, or if the customer made a mistake, use acknowledgement such as "I see that there is a problem. Your order form says you wanted 10 items, and I hear you saying you only wanted to order 7. I am here to help you with getting this resolved because you are very important to us." It's important to remember to give the customer options. Would they want 10 if they got a discount? Do they just want the 7 as agreed upon and you find something else to do with the extra 3?

Sometimes, unfortunately, some people need to vent it all out before they will go into problem solving mode. In this case, use the tips for listening actively: empathize, don't sympathize; and reflect back neutral terms asking for a confirmation.

Finally, there are people out there who are spoiling for a fight. Dr. Stephen R. Covey discusses deal or no deal in his book The 7 Habits of Highly Effective People. These people are trying to get you to agree to terms that are bad for your business. In this case, you need to go for no deal. It's disappointing, but some people are just bored and want to see how far they can push someone. They may not even be interested in buying, but just don't have anywhere else to be or anyone else to bother.

I know it's controversial to say a customer is bothering you. However, if they're in the store to waste their time (and yours) and have no intention of buying anything, they're not a customer. And if they're keeping you from helping other people who are genuinely interested in buying, they're costing you money. However, a key to remember is that they might become a paying customer some day. You need to find the balance between being helpful, and giving a gentle brush off.

One suggestion is to leave them with some information to read while you help & offer to come back in a few minutes to answer any additional questions. If they're not serious, they'll probably leave but at least they'll feel like they were treated well.

If the person is just trying to hammer out a deal that's good for them and not for you. First you can appeal to the customer's sense of fairness that the deal would be bad for your business. If they're still insistent, then you can smile and say "I'm sorry, we are not going to be able to make this deal with you today."

Respect is the key for all upset, angry, frustrating, annoying customers. Today's bad customer could turn into tomorrow's golden egg.