Ketu likes sacred grass, flowers, red lotuses, horse gram, mustard-powder, cow-milk, dates, pineapple, sugar, seven-wick lamp, mid-night prayers, pepper, iron, neem and yam to mention a few. Seven is his favourite number and he should be worshipped on Tuesdays and Sundays. The Beejaakshara Mantra for Ketu is
"OM SRAAM SREEM SROUM SAHA KETAVE NAMAHA"
The ordinary mantra is:
"OM KAYM KETAVE NAMAHA"
Other texts refer to Kethu mantra as:
"HREEM KROOM KRURAROOPINAY KETAVE IM SOUHU SWAAHAA"