Have you read the "80-20 rule"? According to this rule, 80% of your problems are caused by 20% of your customers (or clients, coworkers, or employees). The vast majority of people are kind, considerate, and fair (seriously). However, if you don't have strategies for dealing with the relatively small number of difficult people, it is easy to lose perspective. You may dread the workplace, classroom, or other settings where you have to deal with difficult people.
The first step to deal with difficult individuals is to resist your instinctive response. Your natural response may be to strike back, give in, or break off. If you strike back, you may be able to defeat the difficult person this time, but this "win-lose" outcome may not be in your best long-term interest. If you give in and settle for a "lose-win" outcome, the difficult person will expect you to cave in in the future. This will put you at a disadvantage. The false belief that people will like you more if you do what they want increases the likelihood that people will manipulate you and respect you less. If you "break off," you may lose a potentially valuable client, customer, or employee. Instead of reacting and losing sight of your interests, take a step back and analyze the situation.
The second step is to know your "hot buttons." If the other person's tactic has made you angry or frustrated, don't respond immediately. Pause and say nothing for 20-30 seconds. If you still feel angry, take a short break and leave the room if you can. When your anger has dissipated somewhat, say, "Help me understand why you feel so strongly about this." This makes the difficult person shift from an offensive posture to a slightly defensive posture. This also slows down the process. Never make important decisions when you are angry or frustrated.
Listen to understand the other person's point of view. Agree whenever you can without conceding. Identify your common interests. Behave as if you believe the other person is reasonable and interested in genuine problem-solving. Ask your "opponent" to offer a solution that would allow both of you to achieve your interests. If his "solution" is too one-sided, ask "why" and "why not" to help him find a better solution. These techniques are described in William Ury's book, Getting Past No.
In Coping with Difficult People, Dr. Robert Bramson describes simple techniques that can help you cope with specific difficult behaviors. For example, Dr. Bramson describes the Sniper. This difficult person uses not-too-subtle digs, nonplayful teasing, and innuendo to defeat you. He has a very strong sense of how others ought to think and act. Dr. Bramson suggests the following strategy: "Your comment was somewhat humorous, but I got the feeling that there was a dig there. Is that how you intended it?" If he then says, "What's the matter. Can't you take a joke?", you should reply, "Yes, I can take a joke, but I felt that you intended a dig, and I feel you are making another dig about my ability to make a joke. Is that how you meant it?" The Sniper won't change his behavior, but he will soon find another victim. It works.