From apostolic times, Christians have been guided by general rules so that the worship of God should be ordered fittingly and reverently, and our acting in concert in church is a confession of our unanimity of Faith, and so naturally there are directions about the making of prostrations. Having said this, two things must be borne in mind. First, although in general we act in concert, within Orthodox worship there is no strait jacketting. Not everyone in church behaves in exactly the same manner. On a given day, one person might prostrate more than another, or be moved to do so at slightly different points in the service. Secondly, we must remember that some are old or infirm, and may not be able to make prostrations; we should not judge them if we see them"merely bowing" on a prostration day.
There are canonical and liturgical directions which deal with this subject. The full prostration is seen as a penitential act or an act of the deepest reverence, and therefore on days when the Church is celebrating festively they are in general not enjoined in church.
The twentieth canon of the First Ecumenical Council specifically forbids kneeling, and thus prostrations, on every Sunday (it being the feast of the Resurrection) and on the days of Pentecost, the fifty days between Pascha and Pentecost-Trinity Sunday.
In the Great Fast, prostrations are enjoined by the rubrics in the services, particularly in association with the Prayer of Saint Ephraim and the lenten verses. However, even during this penitential period of the year, no prostrations are enjoined on Saturdays or Sundays. Perhaps as a parallel to the lenten practice, it is general in most parishes not to make full prostrations on Saturdays.
Great Feasts are also joyous occasions and thus it it customary not to make prostrations or to kneel down at their celebration. In this regard there seem to be a number of diverse practices. One never prostrates on the day of a Great Feast or on the leave-taking of that feast.* In some churches we refrain from prostrating on the second day of the feast, if there is a synaxis, as there is for instance for Sts Joachim and Anna on the day after the Nativity of the Virgin. It is also customary not to make prostrations throughout the whole period of some of the greatest feasts, Nativity, Theophany, and Pentecost itself (in this instance, the week-long feast itself, rather than the fifty days which end on Pentecost-Trinity Sunday, although we do kneel, of course, for the Kneeling Prayers on Trinity Sunday Vespers, for the first time since Pascha).
In addition to this, rubrics direct that we cease from prostrations on certain forefeasts. Thus, on 20 December, we are directed that although the Nativity Fast continues, in the forefeast of the Nativity we cease from prostrations. (This means, in effect, that we make no prostrations between 20 December and the leave-taking of Theophany, 14 January.) Also, by a direction appointed on Holy and Great Wednesday, the Prayer of St Ephraim is read at the end of the Liturgy of the Presanctified Gifts, and thereafter, even though it is not yet Pascha, we do not make prostrations again, except before the Winding Sheet (epitaphios, plashchanitsa), because we have already entered into the festal period.
We have noted that in the last days of Passion Week we prostrate before the Winding Sheet, although we are not otherwise making prostrations in church. A similar exception is made on those occasions when the Cross is brought out for the veneration of the faithful: on the Great Feast of the Exaltation of the Cross on 14 September, on the Sunday of the Veneration of the Cross in mid-lent, and, if it should fall at a weekend, on the feast of the Procession of the Cross on 1 August.
We should also bear in mind that the liturgical day (although not the fasting day) begins with Vespers, or more precisely, with the entrance and/or prokimenon at Vespers, and thus we do not make prostrations on a Saturday evening after the Vespers entrance, although we do do so on Sunday evening Vespers, it being a service for Monday.
Lastly and importantly, one must bear in mind that there are certain local practices and variations with regard to prostrations, as also with regard to much else within Orthodoxy. If a practice is not clean contrary to the teaching of the Ecumenical Church and thus a malpractice, there is much to be said for following the practice of the church you are in or visiting. "When in Rome..." If you are in some doubt as to what to do, a good idea is to follow the lead of the celebrant or the senior person present; in doing this you will at least be showing them respect and will be humbling yourself. (The Shepherd, December 1990)
At the Divine Liturgy we make prostrations:
at the beginning of "It is meet and right to worship Father, Son and..."
at the end of the prayer, "We praise Thee, we bless..."
at the end of the prayer, "It is truly meet to bless thee, the Theotokos" (or whatever hymn is used in its place)
at the beginning of the Lord's Prayer when the Holy Gifts are brought out for communion
when, afterwards, the priest, holding the Gifts, says "Always, now and ever..." (except for those who have communed, who should simply bow)
Note: Although prostrations are not enjoined for Saturdays, it is a common practice to make prostrations on that day during the Divine Liturgy at the points indicated above.