Imagine watching a movie
Try not to give what is happening around you events of great importance. Consider that all these processes are a part of a feature film. Imagine that your whole life is a movie. If you can look at the world this way, you will be free from emotions and you will see a more General picture. At the same time you can observe you have different emotions that are pushing you to participate in this film. However, you will only observe, but not to take them.
Stay rational
Try to hide your pride, beliefs and vulnerabilities. Your reaction to events happening around them should be limited to interest. Anger, defense, offense, and other manifestations should stay away. For most people, these actions may seem extremely difficult. For example, if someone encroaches on the system of human beliefs, there is a natural desire to protect them and defend their point of view. To remain indifferent, you must be as open as possible and to allow for the possibility of any development of any situation. If someone disagrees with you, tell him it's his choice and you respect him, but you remain with her.
Keep external calm
If you want to be indifferent, do not show their emotions with facial expressions or gestures. If you're extremely interested in, I can say about it, but don't look with wide eyes and an open mouth. Always keep a natural and relaxed body position as if you are sitting in a chair and watch a movie. Indifference does not imply lack of response as such. You will still need to speak, listen, and act, but not to take other people's words and actions to your account.
React to actions, not words
People endowed with enormous amount of emotion, even if it applies, for example, business. Don't focus on the words of a great value, watch what people do. This will help you to be not only indifferent, but objective. You will not give in to emotions, you will only respond to real action.
Communication, like a stranger
If you want to show their indifference to the concrete person, communicate with him as with a stranger. Do not raise it above the others, not give it more attention than others. You can still talk to him, but when the conversation ends, forget about the person a stranger. This conversation is especially effective if you see a person who you hated and who hated you. Aloof and indifferent conversation, in this case a more powerful weapon than showing any reactions. People will wait for a habitual reactions, and will not know what to do when you leave.