General Circle Information:
Circles have been sources of power for centuries. Old temples are full of circular patterns and gatherings have always taken place in circles. Mysticism surrounded their perfect symmetry (i.e. no matter how you fold a circle through its centre, the two halves will always be perfectly equal). It was considered polite in old times to seat your guests at a circular table as it did not require someone to act as the head of the table. Cicles in magick are often called circles, domes, or cones of power. You can visualise it as a dome or cone.
Creating a circle around the area in which you wish to work creates a sacred and protected space: it both stops your energy seeping out, and stops other energies seeping in.
There are many who don't believe that circle casting is necessary, others believe that it is vital. It really depends on the type of magick you perform. For long and detailed rituals, such as the sabbats or initiations, a circle can be a good idea. You can modify a circle casting to create a banishing ritual in itself (by expanding the circle to fill a negatively charged area). However, if you are like me and use spells all the time during the day to get the traffic rolling and help you with other little things, you'll know that a full casting is simply not practical. You may choose to combine the practices. You can save casting for certain spells that you think it will help with, and leave them for those that don't need it.
Circles casting may also be modified to create general protection domes if you are feeling unsafe. They fade with time, so you don't have to worry about breaking them. A few years ago I was having a really bad time sleeping. The energies in my room were disturbing me too much and I'd lie there wondering what was about to leap out at me. By casting a quick circle of light around myself and my bed I found it much easier to sleep. They usually faded by morning. (In time you will be able to tell when they are still there.)
Circles can also help you focus your intent in order to get a maximum amount of energy, while preventing the area around you from becoming tainted by passing spirits and energies.
There are many, many versions of casting a circle. You can cast circles with specific intentions, or for different times (such as nocturnal circles). Other versions also call the Guardians of the Watchtowers (the four quarters) to assist. I tend not to do this as it seems a little pressumptuous that they'll want to come along. I call them for some things, but it's best not to annoy them. I've heard stories of people who don't dismiss them well and have the pipes in their houses burst as a result. I'll list the way I do it, but feel free to searh for a way that you are comfortable with.
You should also note that you don't have to cast a new circle for every spell you do. You can do as much as you need to in the same circle and just close it when you're done with magick. (Oh, that doesn't mean you should leave it permanently. Just take it down once you've finished working.)
Casting the Circle:
All tools must be within the circles before you begin. It is possible to leave the circle once it is cast, but only if completely necessary. NEVER break it during a spell.
The altar should be set up in front of you. It doesn't really matter which direction the altar faces, but most prefer that you look east for general purposes. For other purposes you may choose to face other ways. (e.g. for money related spells, you might face north. More on this later.)
Light a white candle (this is you altar candle and its best that you always use the same one...of course until it has burnt down completely and you need to buy a new one. This is the only use this candle should have) and meditate or concentrate on what you want to accomplish with you workings. When you are in the right frame of mind, picture you circle forming from the point directly in front of you. This can be on the other side of the altar, or you may wish it to come from the altar candle. Picture it forming clockwise (deosil) all the way around you. You can visualize this as a white light forming a ring or as a circle of flame. Once the circle is complete, visualize the light extending slowly upwards from the circle to form a translucent dome or cone of light around and above you, completely enclosing you inside. It will feel like the inside of a bubble.
Take another minute or two to relax and feel your energy filling the circle. You might wish to visualize this as a coloured smoke to help you feel it better. When you are ready and relaxed, you can start you spell.
Entering & Leaving the Circle:
If for any reason you need to leave the circle once it is cast, you can open part of it and reclose it. Remember: You must NOT do this during a spell. You might have left something outside before you begin or need something afterward.
Simply cut out a doorway opposite the altar either with you hand or your athame.
When re-entering, go through the same doorway. Once you are inside, reseal the doorway by drawing your hands or arms together into an "X" shape, as if pulling curtains closed. Then gesture a pentagram with your right hand over the doorway to seal it.
Closing the Circle:
When the spell is completed and you've had a moment to collect your thoughts and recuperate, you'll need to disperse the circle.
Extinguish any candles you have used during your spells. DO NOT blow them out as this disperses the magick, thus weakening the spell.
Absorb any excess energies that are inside the bubble that failed to be used or focused into your spell's purpose. This will help you revitalize. If you performed the spell properly you will probably be feeling quite exhausted by now. Just visualize this.
Once this is done, see the dome slowly collapsing (starting at the point directly above your head) back into your circle on the floor. Then collapse it anticlockwise (widdershins) into the point from which it was formed. Now extinguish (don't blow this out either) the candle.
The circle is now dispersed and it is safe to leave.
Example Ways to Cast a Circle