"So far the Advent Day of Lord Rama Candra, it should be celebrated as Lord Caitanya's Birthday was done. Fasting up to evening, and then take prasadam, and chant Hare Krishna whole day, and be engaged in reading and chanting off and on, chant for some time, then read for some time, then again have Kirtana and so on, throughout the day. If you have not got a Ramayana, then you can read Bhagavad-gita or Srimad-Bhagavatam, that is all right."
(Srila Prabhupada Letter, March 28, 1968)
Note: If one is unable to fast completely, Srila Prabhupada has recommended an Ekadasi diet of "simply eating fruits" or "no grains, cereals or beans are eaten; simply vegetables and milk are moderately taken, and chanting Hare Krishna and reading scriptures are increased."
.