Moon phases are important to Wiccans. Traditionally, goddesses such as Artemis (new moon/maiden), Hera (full moon/mother) and Hecate (waning moon/crone) have represented the moon's changing faces. Spells that are governed particularly by one of the aspects are often called during the corresponding moon phase.
The Maiden governs the aspect of childhood, new beginnings, spring, new starts and the first menstruation of a girl. The Mother represents maturity and motherhood, the harvest, summer, bounty and strength. The crone governs endings, old age, wisdom, justice and retribution and Magickal mysteries.
Rituals on the full moon are very powerful. Many Wiccans believe that the time of the full moon holds the great bounty of Magickal energy, given to Witches by the Mother. This means all the spells you want to do will be stronger. It is also more likely that the results will happen faster. Personally, I believe that each cycle of the moon holds the same amount of energy but just attuned to different types of Magick. As the Mother strides the wall between youth and old age, the full moon is the best time for general Magick.
A full moon ritual can be very complex. It can have many elements or can just be a loosely tied together group of spells that a Witch wishes to cast. A Witch can also call down the moon. Calling down the moon, means that a Witch calls down the power of the moon and the presence of the Goddess. This can be a very intense experience and I've found it works best with several Witches.
A very basic ritual honors the moon, draws power from it and then uses a spell to focus the granted power. A request of the Goddess instead of a spell can also be done. In this kind of ritual, the Goddess is more present than during some of the others. Due to this, a Witch should take care to be respectful and precise.
Recently, I did a combined Shamanic and Wiccan full moon ritual. It was a very powerful experience and the blending seemed to work really well. I suggest caution though, as sometimes if you don't know the other people well, the ritual can create a discord. Also, make sure the other pagan practitioner is willing to be flexible. The God and Goddess are happy for Witches to practice with and learn from other religions. Just be respectful of both traditions.
Basic Full Moon Ritual
First cast a Circle. The Circle should be fully cast, as major acts of Magick that are required by a full moon ritual, need a Witch's total concentration. It is very difficult to maintain a lesser Circle during major Magicks and could be dangerous to the Witch. Once the Circle is cast, kneel before your alter looking up at the moon and say;
"Lady Moon bright and serene,
Shining with the bounty of the Mother,
Look down on us your Children of the Earth.
Come, light of the Goddess,
Fill us with your power.
Lend us your blessings,
Let your light surround us.
Impart to us your light and blessing.
Your love and grace, surround us.
Surround us Goddess,
Surround us with your love."
Once the moon's energy has been called down, a Witch must direct the granted energy. Sometimes, there will be no direction but only meditation. The energy is then released with the undoing of the Circle into the environment. A spell or series of spells can also direct or use up the granted energy. A request can also be made of the Goddess. She may then choose to use the energy you have been granted, for the stated purpose.
"Power blessed to me by the Goddess,
rise in me for healing,
to replenish and renew my being.
Power blessed to me by the Goddess,
Surround me with strength.
By the power of the Goddess,
So mote it be."
Keep the request formal if you want. A more personal prayer will also be heard if you choose not to set your request into words. If there are others within the Circle who have taken part in the ritual, have them also make their own request. I have also heard of group requests that work just as well. As with many other strong Magicks or major rituals, the rite must be closed.
"Goddess and Spirits,
You have heard our voices,
and our Craft has been completed.
Depart with our thanks and our love,
as we eat these cakes to replenish our bodies,
and this water which shall cleans our souls.
By the power of the Goddess and Spirits,
This Circle is undone but not broken,
So mote it be."
Variations on calling down the moon and working with the given energy are all over the internet. There is no version that is the 'correct' version. The correct version, is the version that makes you feel good. Don't hesitate to make your own or adapt an existing ritual.
In the Shamanistic and Wiccan version that I recently did, the Circle was not formally closed. Instead we worked on a beach and let the sea naturally close and undo the circle. This was according to Shamanistic tradition and I found that it worked very well. I went back the next day and found that the circle was as fully washed away and no residues were left. I have given the ritual closing that we did that night above.