Chin Mudra

The nail of the index finger touches the thumb joint and the other 3 fingers are pointing down to the earth. When the finger touches the thumb, a circuit is produced which redirects the prana (energy) back into the body instead of dissipating into the environment. The three fingers represent the control of the 3 main gunas (characters). These gunas are sattvic (purity, knowledge), rajasic (activity and motion) and tamasic (inertia and laziness).

Om

OM is a sound energy and is written differently in different languages. The vibration of "OM" symbolizes the manifestation of God in form. Om is divided into 3 parts A + U + M wherein A is the start of the sound and hence represent creation, U is the maintenance part and hence preservation and M is the finishing sound and hence represents dissolution. The same 3 parts also represent the three levels of consciousness: waking, dreaming, and deep sleep. Some say that "Aum" is the same as the "Amen" in Christianity and "Amin" in Islam.

Namaste

Namaste is Namah + te. Namah means "I bow" and te means "You" and so Namaste literally means "I bow to you". To do the action "Namaste", Keep the palms together with fingers pointed upwards in front of the chest and bow the head down with closed eyes. The gesture is enough and there is really no need to utter the sound.

Shanthi

Shanthi means "Peace". It is usually repeated thrice as in "Om Shanthi, Shanthi, Shanthihi". It means the threefold peace in body, speech, and mind (i.e. peace in the entirety of one‘s being). It also denotes peace within ourselves, peace with all that is of the earth and peace with all that is beyond the earth.