In Tibetan Buddhist lands the most common prayer, found everywhere, is Om Mani Peme Hung, the mantra of Chenrezi, the Buddha of compassion. The mantra originated in India; as it moved from India into Tibet, the pronunciation changed because some of the sounds in the Indian Sanskrit language were hard for Tibetans to pronounce.
Sanskrit pronunciation
OM MANI PADMA HUM mantra of Avalokiteshvara
Tibetan pronunciation
OM MANI PEME HUNG mantra of Chenrezi

Click here to understand more about Compassion. (many great links off of this page):
http://www.webspawner.com/users/kwanyin

The Twelve Vows To Kwan-Yin Bodhisattva
"I respectfully bow to Kwan-Yin, the Tathagata, with the title Boundless Understanding, the name Great Liberation, who raised the Immeasurable Vow.

I respectfully bow to Kwan-Yin, the Tathagata, of one thought and a mind of no obstacles, who vowed to stay always in the Southern World.

I respectfully bow to Kwan-Yin, the Tathagata, who vowed to stay in samsara, in the realm of darkness, listening to the cries and rescuing sentient beings.

I respectfully bow to Kwan-Yin, the Tathagata, the conqueror of raksas and destroyer of evil spirits, who took the vow to end all troubles and difficulties.

I respectfully bow to Kwan-Yin the Tathagata, who holds the bowl of pure water and willow branch, who took the vow to sprinkle sacred water to calm the mind of humankind.

I respectfully bow to Kwan-Yin, the Tathagata, the great compassionate, forgiving one, who took the vow to practice equanimity at all times.
I respectfully bow to Kwan-Yin, the Tathagata, who day and night is the destroyer of obstacles, who took the vow to destroy the three realms of suffering.

I respectfully bow to Kwan-Yin, the Tathagata, who faces south, diligently practicing, who took the vow to cut all fetters and knots.

I respectfully bow to Kwan-Yin, the Tathagata, the maker of the dharma boat which rows in the suffering ocean, who took the vow to save all sentient beings.

I respectfully bow to Kwan-Yin, the Tathagata, with streamers in front and a canopy behind, who took the vow to guide beings to the Western World.

I respectfully bow to Kwan-Yin, the Tathagata, who resides in the Realm of the Buddha of Unlimited Life, who took the vow to be the helper of Amitabha Buddha.

I respectfully bow to Kwan-Yin, the Tathagata, the honorable one with a body without imperfections, created by the twelve great vows."


Story about Kwan Yin

A very devout follower of the Kwan Yin, Bodhisattva of Compassion, One day, the village in which he lived was flooded by a overflowing river, and the water was rising rapidly. He escaped to the roof top of his house and prayed to the Bodhisattva for help, because according to the Lotus Sutra, when the Bodhisattva of Compassion hears the cries of the world, she will come down to help anybody in despair.

As he was praying to the Bodhisattva, a native Indian rowed a canoe along the flooded river and cried out, "Hi. Fellow, do you need a ride in my canoe?" He did not like natives because most of them are not Buddhist and so he replied, " No. I do not need your help. The Bodhisattva will come and help me out." And he continued to pray to the Bodhisattva.

After a while, an Anglo Saxon American arrived in a speed boat and cried out, "Hi! Do you need help? If you do, just come and ride in my speed boat." But he did not like white people either because most of them are Christians. So he refused his help also.

Next, a helicopter flied above the house and the pilot shouted to him, "Do you want to come fly with me?" But he thought that Buddhist should live a simple life, free from high technology. So he replied, "No thank you. I am sure the Bodhisattva will safe my life, if I pray to her." The pilot left.

Finally, the house gave way to the flood, and he was drowned. After his death he went before King Yama (the God of Hell) and filed a complaint, "According to the Lotus Sutra, the Bodhisattva of Compassion promises to come and save my life whenever I pray to her. Why did she break her promise?"

Did she??... You decide.