The reciting of mantras (which are syllables, words, or texts) has been performed since the Vedas were revealed over five thousand years ago. In Tantra, mantra recitation (also called “japa” or repetition) reaches a grand height. The word mantra itself has several meanings. Manas means mind or thinking. Trana means liberation. Thus a mantra can channel thoughts into liberation. Another interpretation suggests that a mantra protects the mind. Mantras are sounds charged with the power to gain favors, to appease the gods, and to identify with the ultimate reality.
There are countless mantras. Hindu life is surrounded by mantras; from birth to death mantras are chanted. Mantras can be recited out loud, which gains one a certain amount of merit. When the mantras are whispered, greater merit is gained. The highest merit is gained when the mantra is heard silently inside. This silent hearing of mantras must never be rushed or done incorrectly; merit is lost in those cases.
Beyond seeking favors, mantras can be used as an object of concentration, helping to still the mind. Mantras can easily be incorporated into the Yin Yoga practice. A yoga teacher can generally recommend an appropriate mantra for a student to use.  Many mantras include the syllable Om. The Tibetan Buddhist mantra Om mani padme Om is a wonderful way to still the mind. Mantras praising the source of energy, the sun, are quite common and favored. The Gayatri Mantra  is often recited every morning and there are many CDs available with wonderful renditions of this homage to the sun.