This is from my old blog, The Geekie Hellenist.
This is the ritual for Proirosia. This is dedicated to Demeter, the Goddess of the Harvest. Since this is a harvest festival, even though we have most likely harvested here in the States, it’s still an important one. Hope that you can use this ritual and that you enjoy it.
1) Purify the Altar area.
2) Take the barley and say, “As it was done in ancient times. I purify and cleanse this altar with this barley. With this barley I purify this altar and space so that I may give offerings, libations, and speak with glory and respect the gods of Mt. Olympus.”
3) Light a candle and say a hymn to Hestia.
Hestia, you who guard the sacred shrine of the Lord Apollon. The far-darter at goodly Pathos. With soft oil dripping ever from your locks. Come now to this house, come having one mind with Zeus the all wise-draw near, and with all bestow favor upon my song.”
Prayer to Hestia
Hestia, gracious goddess who sits at the heart of each home, who lives in the heart of each one who reveres you, each one who holds you dear, each one who turns to you for strength and harmony.
Hestia, goddess most needful, goddess most serene, goddess most esteemed, the heart of the city is yours as well, great goddess; within your realm are those who serve the state, who work for all the good of all–your blessings fall on the honest, goddess, your wrath on the corrupt, on those who betray their trust for gain. Defender of the householder, guardian of the hearthfire, Hestia, I praise and honor you.
4) Let Demeter know that your here, saying, “Demeter, hear me.” List her titles and then let her know why your here, which is to honor her with first fruits during this harvest festival.
5) Do an invocation to Demeter.
I call to Demeter, great lady of the land, friend of the farmer, sustainer of mankind, daughter of deep-hearted Rhea and wily Kronos, loving mother of rich-tressed Persephone. In ancient times were you honored by country folk above all others; in all the provinces did men and women pray to you and ask your blessing. Goddess, we see your hand in rows of golden grain, in heavy-fruited trees, in fields of scarlet poppies blooming amongst the barley, in the passing of seasons, in the fury of a mother wronged. Demeter, lauded in storied Eleusis, mistress of those cherished mysteries and sacred rites, by your might and your compassion do we endure, do we live our lives. Demeter, I call to you.
6) Do a prayer to Demeter.
Fair-haired Demeter, daughter of nimble-footed Rhea, grandchild of deep-hearted Gaia, mother of bright-eyed Persephone: in you, as in them all, is the soul of the earth.
The golden grain is yours, O Demeter, and the heavy fruited trees, the dark rich soil and the seeds that hide within.
Friend of the farmer, friend of all who rely on your goodness and kindness, your gift of growth, your gift of bread, your gift of all our lives.
Demeter, bountiful lady, with each spring’s greening of the land you give us hope; with each rich harvest that hope is answered.
Demeter, good mother, I praise you.
7) Do a Hymn to Demeter
I begin to sing of rich-haired Demeter, awful goddess —of her and her trim-ankled daughter whom Aidoneus rapt away, given to him by all-seeing Zeus the loud-thunderer.Apart from Demeter, lady of the golden sword and glorious fruits,  she was playing with the deep-bosomed daughters of Oceanus and gathering flowers over a soft meadow, roses and crocuses and beautiful violets, irises also and hyacinths and the narcissus, which Earth made to grow at the will of Zeus and to please the Host of Many, to be a snare for the bloom-like girl —  a marvellous, radiant flower.
(note: the hymn to Demeter is so long that I had to cut this down.)
Give Food Offering, saying, “I offer this food as a sacrifice, to you Demeter.”
8) Say anything that deals with this festival. Since this is the first fruits of the harvest you can say something like, “Goddess Demeter, you who have given to us what we have planted, from the wheat to the vine, we thank you for this blessed harvest and we thank you for the blessings that you’ve bestowed up on us. May you come back and bless our land with fertility and abundant crops.”
9) Pour libations to Demeter . Remember: Hestia gets first and last libations.
10) Pray to her.
11) End the ritual by saying, “Hestia, goddess of home and hearth, to you I offer last of all as a pious mortal should. Tend to those whom I love and guard the houses of the pious. As the gods will it, so it shall be.”
It is so!
Dump the entire container that you’ve poured your wine or grape juice into outside and then that ends it.