The technique of Kriya Yoga has been given by Lord Krishna in Shrimad Bhavad Gita to Arjuna. The technique of Kriya Yoga is so sacred and secret that it can only be transmitted to a student by the Guru only when the Guru gets the directive from the Divine or his/her Guru to give the technique to the student.

Before the technique is transmitted by the Guru to the student, the Guru ensures that the student has become the right vessel to accept, retain, and then transmit to another right vessel at the right time, under the Divine doctrine.
Paramhansa Yogananda ji has given a series of 29 physical exercises to prepare the body for Kriya Yoga. YogiGuru Saugaato taking note from MahaAvatar Babaji, strongly advocates the same.
Lord Krishna himself has kept the technique sacred and secret in Bhagwad Gita by mentioning the technique in only 2 places of the Gita by a single liner.