The South node or Ketu is regarded as a point of difficult Karma from a past life in which the individual furthered his own selfish interest at the expense of others. The South node, on the positive side, can develop strong concentration and mastery of obscure or arcane subjects. Ketu gives sudden and unexpected results for good or bad. On the spiritual front Ketu gives perception, liberation, wisdom and psychic sensitivity in a more genuine way.

The following is the special name (nama) mantra for the Ketu as preceded by it's Shakti or power mantra. It can be used to connect with the planetary deity and to energize all the higher powers of the Ketu. 

The word 'Hum' in above mantra denotes Havana Shakti, the power of offering, sacrifice, destruction and transformation. 

The following mantras are also considered very good for Ketu. You may opt to recite one of the following mantra if you find it comparatively easy to remember.

The mantras are chanted on japa beads of 108 beads per string. They are similar to rosaries.

The Ketu's mantra may be recited 18,000 times and puja performed with mixed flowers and sandal wood within the ascending cycle of the Moon. begin recitation on a Tuesday during the bright half of the Moon.

presence of 'Maha-Mrityunjaya yantra' at the place of recitation may help you in achieving the desired results faster.

Gayatri Mantra for Ketu:

"Om Chitravarnaya vidhmahe, sarparoopaya dhimahi, tanno Ketu prachodayat"

This Gayatri mantra consists of three parts. The first is the chants to the Ketu. The second is the mantra proper. The third is a summary of the mantra's energies.

The Gayatri mantra is chanted at sunrise, noon and sunset. At dawn it is called Gayatri, the youthful form of the Goddess, consort of Lord brahma, the creator. It is called Savitri, the mature form, at noon, the consort of Lord Shiva. It is called Sarasvati, the elderly form, at sunset, the consort of Lord Vishnu.

You may also opt to chant following puranic mantra for propiating the Ketu (17,000 times).

palasa-puspa-sankasam taraka-graha-mastakam
raudram raudratmakam ghoram tam ketum pranamamy aham

"I offer my obeisances to the violent and fearsome Ketu, who is endowed with the potency of Lord Shiva. Resembling in his complexion the flower of a palasa plant, he serves as the head of the stars and planets."