Our universe can be thought of as having two planes of reality: ordinary reality and non-ordinary reality.
Ordinary reality is the physical plane we perceive through our bodily senses. Non-ordinary reality is every place you can go with your eyes closed. Non-ordinary reality is what people who practice magic call the astral plane, and the process of going there is known as 'astral projection.'
To perform an astral projection, one need only to meditate.
Meditation is the act of closing off oneself to outside sources and focusing only on the magic potential of your thoughts. Here's how it's done:
1. Pick your favorite incense and light it. Scents are powerful tools for conjuring memories and emotions, so pick something pleasant and calming to set the right mood. Whatever you pick, use it every time you astrally project until you get better skilled at it.
2. Start by finding a comfortable place on the floor to sit. Sit with your spine straight, your shoulders relaxed, your legs crossed and your hands resting palms-up on your knees.
3. Begin deep breathing. Breathe in slowly through your nose, then hold it in for five seconds. Count each out in your head. Then, exhale through your mouth and hold it out for another five seconds. Do this repeatedly until all background noise and mental static ceases.
Deep breathing helps slow the heart rate, reduce blood pressure, relax the muscles, alleviate pain and clear the mind. It is an invaluable bodily mechanism for reducing stress. It is wise to meditate before any spell casting ritual, but for astral projection it is a necessity.
4. Once you've relaxed, begin your visualizations.
If this is your first time performing an astral projection, you'll need to start by establishing an 'astral temple,' or a home base to enter and exit the astral plane from. Your astral temple need not be a literal temple, nor does it need to be a real place. (Many casters prefer a place in nature, like an open clearing in the woods or a beach.) Wherever it is, an astral temple need only satisfy three qualifications:
a. It must be a place of isolation, far away from other people.
b. It must be a place of harmony, security, beauty and great sentimental value.
c. You must be able to visualize it well.
Picture the desired location of your astral temple in as much detail as possible. Explore it through mental imagery. Pick things up off of tables, or run your fingers along surfaces to appreciate the texture. Once you've firmly supplanted the memory of that place, you have permanently imprinted it upon the astral plane and can now return to it at will whenever you please.
5. To exit into the astral plane, simply leave your temple. Exit through the front door, or come to the edge of the clearing and step into the woods beyond - whatever is symbolic of beginning a journey relative to your personal astral temple.
Astral projection can be thought of as a waking lucid dream. People practicing magic use astral projection to contemplate big decisions, communicate with people over great distances, meet extra-planar creatures (like angels, fey, demons, ghosts, spirit guides, etc.) and generally get away from the hustle and bustle of physical reality.
Astral projection is neither dangerous nor ill-advised. In fact, when we dream, we are entering the astral world through our spiritual forms, or 'astral bodies,' every night!
Everyone knows what nightmares are like; though they are unpleasant, they are unable to harm you physically. Astral projection sessions that lead to 'nightmares' also cannot harm you. They may even be indicative of unattended to emotions, and may therefore prove enlightening.
Astral projection sessions are at their most potent when performed during the full moon, or on a Monday or Wednesday. Monday is associated with the Moon, whose domain is dreamwork and divination; Wednesday is associated with Mercury, whose domain is knowledge acquisition and swift travel. Both are associated with the element of air, which is connected to astral travel and 'higher-order' thought.
Good luck, and blessed be.