This will be an extremely basic explanation of how astral projection works. This is only one of several paths to the astral. Many also use lucid dreaming.
I will break it into three steps. At each step there are countless methods and tricks, and you will need to find one that works for you.
Trance Induction: First, you must be in the right mindset. This is also the first step of hypnosis and most meditation. It may be achieved by breathwork, visualizations, and many other methods. I will include my favorite.
Lay down comfortably, relax, deep breaths. In through nose out through mouth. Focus on one muscle at a time and relax each one from the toes up.
Leaving Your Body: The next step is bilocation, the out of body experience.
Now that you are in a trance state, visualize moving the self without the body. For this you must become conscious that you are not your body. You are a soul wearing a body. A meat suit. Feel where your body ends and you begin. Feel that you are inside your body but not part of it.
Now attempt to move your true self, your etheric body, without moving the meat suit. Starting with a finger is easiest. Once you can do that, slowly sit up out of your body. Look around, stand up and look back at your unoccupied body. You may also be able to see theย โsilver cordโ of energy which connects you to your body when you are not in it. This is how you will be able to find your way back if you get into real trouble.
Enter Another Plane: Now you need to leave this plane for another. There are countless visualizations for this. Stepping through a mirror, climbing a tree, or a mountain. A staircase into the earth for other planes. Some form of crossing a boundary, preferably symbolic of your destination, and with a firm idea in your mind of where you want to go.