There are a lot of different variations on void meditation. Regardless, the basic concept is to reach a state where you let go of everything around you, including yourself, to enter a state of nothingness. It is in this state that we are able to let go of strong emotion, conceptions of who we are, Past trauma, and the millions of labels/ideals we have of how things should be. This enables us to fully calm and center ourselves. It is also wonderful for self work in learning to carry that inner clarity throughout our daily lives. It can also be helpful when we cannot understand something in our lives due to the constant clutter that is the human mind. Great practice before doing any ritual, in my opinion.
Strong word of caution. I do not recommend spending too much time in the void, as a means of coping with emotional issues or stress. While it is good to learn to control the heavy traffic that can be our minds, we must also learn to be in the present moment. If that is an issue for you I highly recommend learning about mindful meditation.
I personally like to use a black mirror for void meditations. If you do not have one, you can simply paint a reflective surface such as glass with black paint. I used a pie plate for my first mirror, painting the back so that it still slightly reflects.
To start I would sit somewhere comfortable where I would not be disturbed. Dim lighting is preferred. Place the mirror in front of you and focus on the area between your eyes. Try to breathe in a deep steady rhythm, letting any thoughts that come pass without grasping onto them or adding to them consciously. Keep focusing on that dark space, until it feels as though the world around you falls away. All you can see is that empty black space around you. Unlike Ap and other forms of projection, do not try to visualize yourself within that void, but simply nothingness.
In this space, you do not exist. The world around you is gone. Your stresses are gone. You do not feel any specific temperature, nor any other sensations. You feel as though even time has gone. Let go of any concept of who you are.
This meditation can be difficult for some to do. If you find yourself having difficulty pulling out of such meditations I suggest setting a graduated alarm. Something that slowly goes from quiet to loud. Allow yourself ample time to come out of the state and slowly back to the here and now. If you cannot achieve this state the first time do not be discouraged. With time and practice anyone can do it. Everybody is different.
I hope that you find this meditation to be useful to you. Feel free to share if you have your own means of getting into the void. I absolutely love hearing others experiences :)
Love, light and blessings