This ritual was found in Kate West's The Real Witches' Handbook, though I have altered it somewhat. I really like her books, they are down to earth and explain many things in a simple, uncomplicated way.
The key themes of
this Sabbat are the peak of the Sun’s power and the start of its
decline, the changeover from Holly King to Oak King and the Goddess as
Mother, pregnant with the harvest to come and presiding over the changes
of the seasons.
Preparations
Before doing this ritual, you should have a clear quartz crystal with a hole through it. Quartz crystal is best, but it can also be lead crystal or cut glass. It doesn't have to be very expensive, but do shop around for your crystal. Once you have your crystal, thread it onto a 24 inch piece of string, knotting the string to secure it.
Cleanse the crystal, physically by washing it in warm soapy water. Then cleanse it psychically by running it under cold running water for five minutes, visualizing all imperfections being washed away.
Cast the Circle
When you are ready cast the Circle.
Take up the Athamé and facing East, the direction of the Rising Sun, take a moment to center yourself and begin to cast the Circle. Visualize a white light coming from the tip of the athamé and with arms straight out, turn the blade point out, slowly turning clockwise the light following you.
When you return to the East bring the athamé back to you and say:
“As above, so below.”
As you say this, visualize the light going above you and below you forming a perfect sphere.
Take your crystal and hold it in the light of the Sun. Don't worry if it's cloudy outside, the Sun is just as present. Visualize the Sun's rays filling the crystal with light and energy. When you feel the crystal begin to warm and can feel the vibrations from it, it has been charged, hang it in the window, preferably where it will be sure to catch the Sun's rays.
At any time when you feel in need of the energy of the Sun, you can take your crystal down and carry it with you, or wear it on a necklace around your neck.
Thank the Goddess and God
Thank the Lord and Lady in whatever manner is appropriate for you.
Close the Circle
Release the Circle and ground the excess energy into the Earth.