Dear Monica, I serve as deacon in the ROC in communion with Rome (Russian Greek-Catholic Church). The extent of fasting before receiving Holy Communion is normally settled by your spiritual father or confessor (or the priest of the temple where you will attend), to suit your particular spiritual situation. As is the need for Confession each time and attendance at Vigil prior, and the recommended akafists/canons/prayer rule as preparation - and, indeed, when and how frequently you commune in the first place. As a very general rule of thumb, for a communicant blessed to receive frequently (eg, weekly), the fasting requirement may not be as onerous as three days. Some of these traditions are aimed rather at less regular Christians, who may benefit from a longer, specific preparation. For example, those who regularly observe the weekly Wed / Fri fasts and try to attend Vigil may not be required by their spiritual father to fast further on the days prior to receiving Holy Communion, but only from midnight prior. I hope this is helpful and not confusing.
Anton