Briefly, how should an Orthodox Christian prepare for Communion: 1) examine oneself, as St Paul commands, before receiving—look at your sins before God, your neighbor, the Church and yourself. 2) Confess your sins before the Priest, in the Holy Mystery of Confession if you have sins. 3) Forgive everyone, ask forgiveness of those whom we may have or have offended. 4) Pray the Pre-Communion Prayers, found in the Prayer book. 5) Attend Vespers the night before receiving Holy Communion. 6) Keep a total fast from midnight (as well as the weekly Wed/ Fri abstaining from dairy and meat and the fasting seasons), unless you have medical reasons to do otherwise. 7) Always always remember that Holy Communion is a Gift to us from God, the most precious Gift upon the earth.
The document on Confession and Communion is available at the following website:
You may say, "this list is TOO LONG!" Holy Communion is the "Medicine of Immortality", the "Provision for Life Eternal" the "burning coal of divinity" the very presence of Christ, in the form of bread and wine. Our reception of It is for the union with God, our co-union with ALL in the Church—those gone to their eternal rest, our grandparents, the saints, the Mother of God, all of the Church for all time; It is the participation at the Mystical Supper in the Upper Room with the Holy Disciples, that SAME Supper of Holy Thursday; It is the cleansing of our sins; the illumination of our souls, and much more. If one cannot prepare for such a marvelous and mysterious mingling of God and man, then, probably, one should not dare step up to the Chalice. The very purpose of our life is linked with how seriously we take our participation in the Eucharistic feast, since the purpose of our life is to be cleansed of our sins so that we might be joined with God, and to be the "light of the world".