Not only will the Magick energy sent out be more powerful if you build it up within the circle, but the circle itself will protect you from negative thoughts and energies while you do your Magick spell work. If your focus is not in the right place when you cast a circle, any Magick you do can be ineffective and whats worse, you can leave yourself open to negative energies tainting everything you do. Thats why it is so important to cast a circle in the right way, and you have an advantage as a beginner. You can start with a clean slate, and learn to do it right the first time. Read and learn as much as you can and have fun with it. Good luck.
Have everything set up and in easy reach first so you don't have to break your concentration during the process. Think about how you're going to build the energy up and release it to accomplish your goal.
It always pays to check the timing of the spell astrologically. This applies more so for waxing/waning lunar cycles where I always think its advisable to check which of the mansions of the moon will be occupied.
The moon is progressing into Scorpio I believe which can be an interesting one depending on what energy you're working with.
Relax. Energy doesn't flow well through tense muscles or a tense consciousness.
Control your breathing. (This will also help you relax.) remember to draw energy in when inhaling and send it out when exhaling. Energy follows the breath.
Focus your mind on what you are doing and don't let it wander to what you did today, what you are going to have for dinner, how work or school will be tomorrow, etc. Remember, where your awareness goes, your energy flows.
Casting your circle, or opening your temple, creates your own space, seperate from the rest of the Universe where you can do your work in. It's a very important tool. Treat it like it is, with care and respect, and you will have the best effects from it.
