The Winter Goddess, Cerridwen

Since I'm into the celtic pantheon, I think it's fitting to call upon them in times of need and honor. On the Winter Solstice, I will be joining my fellow witch sisters in a ritual to celebrate the coming winter. I can't describe what we will be doing but we are allowed to call upon a goddess to join us in the ritual. I'm choosing to call Cerridwen to the ritual.

This is Cerridwen's Story From Order of the White Moon:
Cerridwen was originally worshipped by the people of Wales. It is told that she lived on an island, in the middle of Lake Tegid, named after her husband, with her two children, a beautiful daughter, Creidwy, and a very ugly son, Afagdu. To compensate her son for his unfortunate appearance, Cerridwen brewed a magickal formula, known as "greal", which would make Afagdu the most brilliant and inspired of men. For a year and a day, she kept six herbs simmering in her magickal cauldron, known as "Amen", under the constant care of a boy named Gwion.

One day, while Gwion was stirring the cauldron, a few drops of the bubbling liquid spattered on his hand. Unthinkingly, and in pain, Gwion, sucked his burned hand, and, suddenly, he could hear everything in the world, and understood all the secrets of the past and future. With his newly enchanted foresight, Gwion knew how angry Cerridwen would be when she found he had acquired the inspiration meant for her son.

He ran away, but Cerridwen pursued him. Gwion changed into a hare, and Cerridwen chased him as a greyhound; he changed into a fish, and Cerridwen pursued him as an otter; he became a bird, and she flew after him as a hawk; finally, he changed into a grain of corn, and Cerridwen, triumphant, changed into a hen, and ate him.

When Cerridwen resumed her human form, she conceived Gwion in her womb, and, nine months later, gave birth to an infant son, whom she, in disgust, threw into the water of a rushing stream. He was rescued by a Prince, and grew into the great Celtic bard, Taliesin.
They also have a explanation of what she represents in more detail on their site, Cerridwen. I don't want to copy the complete page, the story should be enough. Another site I've found is called Goddess Guide, summarizes of symbolism.

Areas of Influence: I'm often asked how to pronounce Ceridwen? (Ker-RID-Wen) so I thought it would be useful to include that piece of information on this page. Other spellings of her name include Caridwen, Cereduin, Keridwen and Kerridwen. Her name is derived the Celtic word cerru meaning cauldron which like the Goddess herself, symbolizes the transformative power of magic, wisdom, rebirth and creative inspiration. For these reasons she is seen as a patron Goddess of witches and wizards. She is also associated with the moon, fertility, science, prophecy and poetry.
The Cauldron and the dark moon are associated with this Goddess.

Sacred Animals:
This Goddess often transformed into a white sow to address her people.
In her myths she also shape shifted into a greyhound and an otter
Sacred Birds: Hawks and hens.
Sacred Plants:Corn.
Evocation (Lazy Witch)

Cerridwen, keeper of the Cauldron of Awen,
I invite and welcome you to this circle.
I call to your transformative spirit
and ask for your power, wisdom, and inspiration to be shared with me.
Blessed be. 
 It took me quite a while to find some suggesting for offerings because everyone had information on her story but not on how to honor her.
Cerridwen’s symbols are the cauldron, pigs and grain. You can prepare a meal of pork and wheat in her honor. Alternatively, you may wish to forego pork and wheat for a period of time to show reverence to her sacred symbols.
I've also read that you can offer grain in a offering bowl and whisper what you desire until the end of the day. After that, you will pour the grains outside for the wildlife to gather and carry to the goddess.

Prayer (Awaken The Goddess Within)
[Note: This is best done right before bed]
Cerridwen, Goddess of Inspiration, Knowledge, and Power
Knower of the Unknown
Hear my Prayer
[Describe your problem]
I know the answers I seek are within me, but they are clouded behind veils of misperception
Please push back the veils and reveal them to me.
[Sit for 15 minutes and see what Cerridwen reveals to you. If the answer you seek doesn’t come in that time frame, you may sit longer or go to sleep knowing the answer will come to you in a dream. Remember to thank Cerridwen before you go to bed and again once the answer comes to you.]