Although there are many techniques for quieting the mind, such as reflection, deep breathing, contemplation, and visualization, the most universally accepted and most used technique is meditation. In as little as five to ten minutes a day, you can train your mind to be still and quiet. This stillness can be incorporated into your daily life, making you less reactive and irritable, and giving you greater perspective to see things as small stuff rather than emergencies. Meditation teaches you to be calm by giving you the experience of absolute relaxation. It teaches you to be at peace.
There are many different forms and variations of meditation. Essentially, however, meditation involves emptying your mind. Usually, meditation is done alone in a quiet environment. You close your eyes and focus your attention on your breath - in and out, in and out. As thoughts enter your mind, you gently let them go and bring your attention back to your breath. Do this over and over again. Over time, you'll train yourself to keep your attention on your breath as you gently dismiss any stray thoughts.
You'll quickly discover that meditation isn't easy. You will notice that your mind will fill with thoughts the moment you attempt to keep it still. It's rare for a beginner to be able to focus attention for more than a few seconds. The trick to become an effective meditator is to be gentle on yourself and be consistent. Don't be discouraged. A few minutes each day will reap tremendous benefits, over time. Or, if you prefer, you can learn from a book, or better yet, an audiotape. (It's hard to read with your eyes closed). My favorite resource is Larry Le Shan's How to Meditate, available in both book and audio format. I don't know many people I would consider to be at peace with themselves who haven't spent at least a little time experimenting with meditation.