Summarize this article:

Triangle instruments come in different sizes and materials, made of many different kind of metal alloys.  Choose a triangle whose sound fits best with the kind of music you will be playing. You can make any triangle very loud or very soft. You can strike the triangle in different places to get a small range of sounds, described as "lighter" or "darker" and "thin" or "full." Make sure that the triangle is not in danger of falling while being played.  If you are holding it with a string, keep your fingers in an "O" shape, allowing the string and triangle move freely. Alternately, use a triangle holder. A triangle holder is a wooden or metal device that you can use to suspend the triangle. Whether you use a triangle holder or just your hand, make sure none of your skin is touching the metal of the triangle. Contact between the triangle and your skin interferes and dampens the sound. In this position, you can see the triangle, your music, and the conductor if you are in a performance. People in the audience will enjoy seeing your performance, so try to smile, especially if you have a triangle solo!

Summary:
Choose a triangle. Hold the triangle securely. Do not touch the hanging triangle. Hold triangle with bent arm at, or just below eye-level, about one foot away from your face.