In the Lam-Rim teachings there are six methods given to purify karma:
* reading the profound sutra texts
* meditating on emptiness
* reciting powerful special mantras
* making holy objects such as statues, stupas and scriptures
* making offerings to the Guru-Triple Gem
* reciting the powerful Buddhas - holy names
Reciting The Sutra of the Bodhisattvas - Confession of Downfalls is an extremely powerful purification practice in which one recites the names of the 35 Buddhas of Confession. By reciting the names of the different Buddhas, one purifies specific various negative karmas. By reciting the name of just one Buddha, such as that of Guru Shakyamuni Buddha, one purifies the negative karma of 80,000 eons. This is an extremely powerful practice, especially if one recites the names of the Buddhas while prostrating. Thus, through the practice of these purification practices, one can experience the positive results in this life. Reciting this mantra it purifies today's and past lives' negative karma.
http://www.blia.org/english/publications/booklet/pages/37.htmReciting the Buddha’s Name:
Many people are distressed by anxiety, agitation, improper desires, and delusional thought. These torments not only disturb our psychological well-being and eventually take a toll on our physical health, they also hinder our ability to perceive the truth of life and attain enlightenment. When we recite the name of the Buddha, the torment of improper and delusional thoughts will cease and our mental anguish will evaporate. The heart calms down, the mind is awakened and purified, and no greed, anger, ignorance, or other toxins will arise, thus giving us greater protection from illness and delivering us from our ignorance. Reciting the Buddha’s name also helps us to reduce our bad karma, eliminating as many misdeeds as there are grains of sand in the Ganges.
A Buddhist saying tells us, “Reciting the Buddha’s name once can diminish one’s bad karma, and bowing to the Buddha can increase one’s good karma.” Thus, reciting the Buddha’s name is an effective practice for healing the distress of our minds and bodies, as well as benefiting our cultivation and awakening us to the truth of life.