Man in Sanskrit means mind, and Tra means liberation. So mantra literally means liberation of the mind. The mantra is a sound vibration which, when delivered correctly, has a powerful effect on our body and mind. It calms our mind and senses, relax the body and connects us to higher energies, because their vibration causes the cleaning of lower vibrating energies. The mantra is definitely a word of power, a sacred word that must be used properly and conscientiously.
Mantras are sacred sounds that help you enter a state of meditation. Endued with great energy force, they also help us to fulfill our desires. To function well, should practice them regularly, since we are worthy and fit for this - each day or at least every other day. A mantra should be repeated 8 or 108 times, but the cases in which a repeated many times, or more than seven times, mantra loses his power and in other cases should only be used in eminent danger, because we should not use the name of God in vain. The correct pronunciation is very important for him to prove effective, because the mantras are in Sanskrit, the sacred language of the Hindus. Thus, where the letter h appears, repeat as if rr. Except in some cases where j is exhaled.
The power of the mantra lies in its correct intonation and proper mentoring.
The best known of mantras, OM flees to all grammar rules exposed as it is considered the synthesis of all sounds.

Exist in the Indian tradition hundreds of mantras and the use of each has a specific purpose. For those who want to start in this practice are some indications:
Sit in a comfortable position and try to relax your breathing by concentrating on the abdomen. Next, vocalize the mantra for a minimum of three minutes. This is the most advisable way to enhance the mantra, but if you can not say it aloud, whisper it or just mentalize it.