We acquire karma by our actions, therefore we must perform good actions towards others in every possible way, including service to others, to reduce it. Mother Teresa is a great role model for devoting a whole life to service to the Divine by serving other people. In our own lives, the small actions of loving kindness by smiling at others genuinely, encouraging others, helping strangers in small ways help both us and the strangers. One of those ways more thought related is to pray for others.
It is an odd habit in humanity that so often the people we are meanest to are our family members, whom we purport to love. Loving kindness definitely begins at home.
Karma is like a clump of negative matter in us. The great sages and seers have given us mantras to chant. Mantras work to ameliorate our karma by breaking up those clumps of negative karma within our Chakras 1–6. Each of the 50 sounds in the Sanskrit alphabet, the Matrika, stimulates a coordinating petal on a particular chakra, thus sanding off a minute bit of karma. A lot of chanting = a lot of sanding, so to speak.
Different mantras work differently in their sound vibration pattern to help us. Some, especially Rama mantras, work to heal us in body and mind. Some mantras are liberation mantras, meaning they are so potent that they reduce our negative karma quickly. Mantras for each of the 9 Planets of Jyotish astrology work to reduce our parabdha karma, that which we are born to work out as expressed in our natal chart. Each planet has different parts of the body that it rules, so if there is illness or planetary conflicts in our natal chart and progressed chart, chanting the planetary mantra to alleviate those conditions is very beneficial.
The Gayatri Mantra is the master mantra, the one that contains all the vibrations of the entire universe.
“Of all mantras, the supreme and the most potent power of powers is the great, glorious Gayatri mantra. It is the support of every seeker after Truth who believes in its efficacy, power and glory, be s/he of any caste, creed, clime or sect. Gayatri is an impregnable spiritual armor, a veritable fortress, that guards and protects her votary, that transforms one into the divine and blesses one with the brilliant light of the highest spiritual illumination.” Sadguru Sant Keshavadas writes in his book, Gayatri, The Highest Meditation.