Whenever the mind starts spinning negative or obsessive thoughts, counter-spin! That is the visual lesson of the Tibetan prayer wheel. It is not some magic instrument, but a tangible reminder that it is our own afflicted mind that sets thoughts spinning. Aligning ourselves with the Buddha-aspect embodied in the mantra, we can reverse the process.
Prayer wheels are devices for invoking, establishing, and spreading spiritual blessings and well being. Rolls of thin paper imprinted with a mantra (usually, but not necessarily, om mani peme hum) tens, hundreds, thousands, or even millions of times, are wound around an axle in a protective container, and spun around. Typically, larger decorative versions of the syllables of the mantra are also carved on the outside cover of the wheel.
Reciting mantra, aloud or silently, invokes and awakens specific aspects of Enlightened Mind, our own true nature. Viewing a written copy of the mantra has the same effect, as does spinning the written form of the mantra around in a prayer wheel. This is not superstition, but the simple application of practical knowledge of the working of the mind. The power of the mantra is not external; it is the attention of our own mind to the pure characteristics that we wish to cultivate through internal association.
Prayer wheels are always spun clockwise, as viewed from above, for several reasons: clockwise turning rotates the syllables of the mantra so that they pass a viewer in the order that they would be read; it follows the direction of the sun; and it matches the clockwise circumambulation of stupas.
Practitioners who feel stronger affinity to mantras other than om mani peme hum can construct prayer wheels with the mantras that mean the most to them. Prayer wheels are spiritual technology, and can be applied according to need.