Casting A Circle
Casting a circle is an essential part of any ritual or magickal working.  It serves to create a sacred space that can be used for holding rituals, working with deity and casting spells.  There are many ways that a circle can be cast, some are very complex, others simple, some involve many magickal tools and others require only the mind.  I find it is nice to try out various ways and techniques until you find one that seems to suit you most.  Below I have summarised the stages in casting a circle followed by an explanation of each stage.
*Casting a Circle Step By Step*

1.  Prepare space and tools (if any) needed.
2.  Cleanse the area.
3.  Creating the circle and Calling the Quarters.
4.  Invoke the Goddess and God.
5.  Perform ritual/magick working.
6.  Close the circle.
Step One - Preparation.

Traditionally, magickal circles are supposed to be nine feet in diameter but its not exactly easy to find that amount of space!!  Instead use an area which is big and comfortable enough for what you want to do.

The altar is usually set up facing north and a marker, such as a coloured candle or crystal are placed in each of the four compass points of the circle.  Thus, marking out the boundaries of the circle.

Before casting the circle it is best to have a ritual shower or bath to prepare yourself.  See here for details.

Step Two - Cleansing the Area.

This can be carried out by using a broom to "sweep" the area clean of any negative energies.  Another easy way is to use salt and water to purify the circle by sprinkling it over the area to be used.

Step Three - Creating the Circle and Calling the Quarters

I usually start by invoking the element of Air at the East point of the circle (some place Air in the North).  I light the candle representing Air and say a few words asking the element to join me.  Then, I work from South (Fire) to West (Water) and finally North (Earth).  As I invoke each element I visualise the circle forming of white light until it is completed.

Once the circle is completed, I often say a few words such as:

"The circle is cast and consecrated,
That the Goddess and God may dwell,
With their child, in perfect love and prefect trust."

Step Four - Invoking Deity.

This is the stage where I ask whatever deities I am working with to attend and guide me in the actions I am about to perform.

Stage Five - Ritual or Magick Working.

Now, I perform the ritual or magick working that the circle was cast for.

Stage Six - Closing the Circle.

I start by thanking deity for attending and biding them farewell.  The same is then done for each of the elements (work in reverse i.e North to East).  Finally, I state that the circle is open and visualise the white light disappearing.