In the comments under the post below this one, Irenaeus asks about prayers for this feast day. I can think of no better one than the beautiful ancient prayer, the Angelus:
Traditionally this prayer is said at six a.m., noon, and midnight, but I think it would be appropriate to pray any time of day especially on this beautiful feast day. While, as this site says, the history of the prayer is hard to trace, the custom of praying a triple repetition of Hail Marys at at least two of these hours is at least seven hundred years old.
The Angel of the Lord declared to Mary:
And she conceived of the Holy Spirit.
Hail Mary, full of grace, the Lord is with thee; blessed art thou among women and blessed is the fruit of thy womb, Jesus. Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death. Amen.
Behold the handmaid of the Lord: Be it done unto me according to Thy word.
Hail Mary . . .
And the Word was made Flesh: And dwelt among us.
Hail Mary . . .
Pray for us, O Holy Mother of God, that we may be made worthy of the promises of Christ.
Let us pray:Amen.
Pour forth, we beseech Thee, O Lord, Thy grace into our hearts; that we, to whom the incarnation of Christ, Thy Son, was made known by the message of an angel, may by His Passion and Cross be brought to the glory of His Resurrection, through the same Christ Our Lord.
There is a society devoted to the Angelus, made up of Catholics, Anglicans, Lutherans, Methodists and other Christians who have a devotion to this prayer. And no mention of this lovely devotion would be complete without a look at Jean-Francois Millet's famous painting of it being prayed, from 1859:
God bless you all as we celebrate this beautiful feast!