For Ketu related problems and during the Dasha or AntarDasha of Ketu:
1. Worship Lord Ganesha.
2. Recite Ganesha Dwadasanama Stotra and Shiva Panchakshari Stotra.
3. Japa of the Ketu Moola Mantra:
Om shram shreem shroum sah ketave namah
Jap should be done 7000 times in 40 days and the pooja should be performed with ash colored flower and sandal.
4. Recite the Ketu Stotra:
Palasha pushpa sankaasham taraka graha mastakam
Roudram roudratmakam ghoram tam ketum Pranamamyaham.
5. Donate: A black cow or black mustard seeds, goat. blanket, weapons made of iron, sesame, dull brown colored items, limes etc. on Thursday. Offer usual food articles to dogs and sour things to female children below the age of nine years. Feed Brahmins (or poor people) with rice cooked with cereals. Donate a blanket to a temple esp. if progeny is affected.
6. Service and being kind to elderly/old people and saints. Not telling own sorrows or secrets to others (esp. when Ketu is the cause of that).
7. Fasting to be done on Thursday.
8. Pooja: Ganesh pooja.
9. Rudraksha: Wear a 9 Mukhi Rudraksha.
10. Wear Gemstone related to Ketu i.e. Cats Eye.
11. Recite 50th chapter of Ayodhya kanda from Valmiki Ramayana.