Ekadasi is a powerful opportunity for us, the souls trapped in material existence, to perform recommended austerities and make our way back to our original home in the spiritual sky. The spiritual atmosphere is infused with selfless devotional feelings of the pure souls for Lord Krishna and His devotees. Enlightened humans should make best use of the opportunity to invigorate in themselves, this pure Vaikuntha consciousness transcendental to the debilitating impurities of the material atmosphere.
His Divine Grace A. C. Bhaktivedanta Swami Prabhupada has given some simple principles for observing all Ekadasis
“One should observe fasting on Ekadasi day, the eleventh day after the full moon and the eleventh day after the new moon, when no grains, cereals or beans are eaten. Simple vegetables and milk are taken in moderate amounts, and chanting of Hare Krishna, reading Scripture, etc. is increased.”
Excerpt From: His Divine Grace A.C.Bhaktivedanta Swami Prabhupada. “Teachings of Lord Chaitanya.” Part I, Chapter 12
“In the Bhakti-sandarbha, by Śrīla Jīva Gosvāmī, there is a quotation from the Skanda Purāṇa admonishing that a person who eats grains on Ekādaśī becomes a murderer of his mother, father, brother and spiritual master, and even if he is elevated to a Vaikuṇṭha planet, he falls down. On Ekādaśī, everything is cooked for Viṣṇu, including regular grains and dal, but it is enjoined that a Vaiṣṇava should not even take viṣṇu-prasāda on Ekādaśī. It is said that a Vaiṣṇava does not accept anything eatable that is not offered to Lord Viṣṇu, but on Ekādaśī a Vaiṣṇava should not touch even mahā-prasāda offered to Viṣṇu, although such prasāda may be kept for being eaten the next day. It is strictly forbidden for one to accept any kind of grain on Ekādaśī, even if it is offered to Lord Viṣṇu.”
Excerpt From: A.C. Bhaktivedanta Swami Prabhupada. “Sri Caitanya-caritamrta – 1975 Edition” Adi 15.9 Purport