Go to the altar, focus on drawing the energy from around and above you, into your body. Feel it pulse and tingle in your body. Send it down your arms and through your athame. Visualize energy coming out of your body and forming a sphere around you. This energy is seen as a white or blue light, or like heat you would see coming off the raod in the summer. According to the season you may outline the edge of the circle with flowers, pine cones and boughs, grain, candles, etc.
If others are outside waiting to be admitted, cast a doorway to bring them though, remembering to close it when all are admitted. Strengthen the circle with the elements by asperging the circle and other coveners with the salt water that was cleansed before casting. The incense and altar candle are also carried around the perimeter. Now the Watchtowers are called, the Goddess and God are invoked and the rest of the ritual begins.