In Eucharistic Prayer I, or the Roman Canon, the prayer Te igitur (We come to you, Father) is said by the principal celebrant alone, with hands extended.
It is appropriate that the commemoration of the living (the Memento) and the Communicantes (In union with the whole Church) be assigned to one or other of the concelebrating priests, who then speaks these prayers aloud, with hands extended.
The Hanc igitur (Father, accept this offering) is likewise said by the principal celebrant alone, with hands extended.
From the Quam oblationem (Bless and approve our offering) up to and including the Supplices (Almighty God, we pray that your angel), the principal celebrant alone makes the gestures, while all the concelebrants speak everything together, in this manner: The Quam oblationem (Bless and approve our offering) with hands extended toward the offerings; The Qui pridie (The day before he suffered) and the Simili modo (When supper was ended) with hands joined; While speaking the words of the Lord, each extends his right hand toward the bread and toward the chalice, if this seems appropriate; as the host and the chalice are shown, however, they look toward them and afterwards bow profoundly; The Unde et memores (Father, we celebrate the memory) and the Supra quae (Look with favor) with hands extended; From the Supplices (Almighty God, we pray that your angel) up to and including the words ex hac altaris participatione (as we receive from this altar), they bow with hands joined; then they stand upright and cross themselves at the words omni benedictione et gratia repleamur (let us be filled with every grace and blessing).
The commemoration of the dead (Memento) and the Nobis quoque peccatoribus (Though we are sinners) are appropriately assigned to one or other of the concelebrants, who speaks them aloud alone, with hands extended.
At the words Nobis quoque peccatoribus (Though we are sinners) all the concelebrants strike their breast.
The Per quem haec omnia (Through him you give us all these gifts) is said by the principal celebrant alone.