The non-dual experience is simply to directly experience one's self and the world as Consciousness without the use of the mind and senses. There are various means to recollect this experience, which is what and who we always already are. There are apparently 2 directions you can take.
One of them is to talk it out, compare notes, compare teachings, and hope for the best, a sort of existential approach, lively and intellectual, like reading Henry Miller, Albert Camus, Jean-Paul Sartre, hanging out, so to speak, with like-minded chums, who like in the lively days back before television, sat around (now over chat-rooms) mulling over in consideration of all the proponents of the idea of non-dualism and discussing what it could possibly be - good fun. (facetious)
In actuality, in every Religion and related philosophies and yogas, there are many, study groups, which in any case develop insight, devotion and proximate perception of the Truth that usually culminates in the experience of "hearing." However, the effect is usually much greater when people are also talking about the lives of the Saints, Sages and Saviors, when they discuss their sacred Words and Teachings, such as Buddha, Christ, Krishna, Rama, Moses, Guru Nanak and the Ten Sikh Gurus, Milarepa, Maher Baba, Ramakrishna, Ramana Maharshi, and so on, because their lives represent the Reality of who we really are, giving substance and meaning and the power of emotion to so transform the mind into a state of purity, that the Inner Self, apparently hidden, awakens and recollects Itself in an experience the Sages call "hearing."
Apart from the reading, discussing and commiserating about the subject of non-dualism, the other approach, is to take up practices that clear out the false or mistaken ingrained identification of one's sense of self or "I" that results in the an emergence from a kind of progressive amnesia with the experience of single pervasive Consciousness.
In this experience, there is no subject object dichotomy, as there is apparently with the mind and the senses. Initially, when one awakens to or begins to recollect and experience one's Self as Consciousness Itself, the use of the mind and senses are abated. You still see them, like one sees a full moon in a crystal blue sky, but you no longer need the light of the moon to see, as the Sun of your Self has risen.
Looking at these choices from different perspectives, but focusing more on the practice to eradicate this progressive amnesia….
What happens through the reading and rereading of non-dual texts, various types of meditations etc. are the occasional "grokking" of the experience, which Buddhists call a "Satori."
A Satori is a sudden flash of pure consciousness.
To experience oneself as consciousness means, simply, that the use of the mind as an instrument of seeing and knowing, as well as the mind's focusing power of attention, and the use of the senses to see and know, come under abatement, and for a while one experiences oneself as a field of consciousness. This is also why Krishna describes the body as a "field."
These Satori's are actually quite common. They don't come just as a result of solving the Koan Riddle. In Christianity and really all householder oriented religions there is an admonishment to persevere in one's life regardless of circumstances and to orient oneself to excel in whatever talents and abilities one has, for example Christ's Parables of the sower and the talents.
As the artist, the businessman, the military man, the holy man, the journeyman laborer, any people with any vocation or avocation exert effort to excel regardless of circumstances in other words to resolve and overcome barriers in their path, there is a continuous flashing of awareness throughout the nervous system to the point where the nerves are so irradiant with these flashes of intuition in persevering that there arises a sudden experience of the seer prevailing without the attention to objects, an experience, which over time does not diminish and instead draws the person's mind inwards, while the body's nervous system becomes brighter and brighter, and the mind more and more intuitive, single, inward drawn. There's a sensation of listening to soundless sound with such an intensity that one remains undistracted even in a crowd, even as one goes about one's daily life.
Many people that have this experience don't know quite what has happened to them, but as it emerges out of the intensity of their lives they tend to realize it as the presence of their own being and abiding in it persevere in their lives, lives that center around taking a stand in Truth and their Word.
In the practice of spiritual meditation, there needs to be the same sense of urgency and determination to "figure out" the experience proclaimed by the Sages, Saints and Saviors, which also requires a total belief and resolution, therefore, to "break on through" with the same intensity as the life experiences mentioned above, or the process will be long and remain unresolved.
As these Satori's flash in the mind over and over, the Truth of one's being begins to take hold.
It should be understood that Consciousness is not something that has to be discovered, it is where and who we are already. This becomes quickly apparent with practice. Then starting from this perspective and belief, it is clear then that the mind is illumined by and within the "field" of consciousness and that in turn the senses are illumined by the mind. This also means that all we see and know is seen and known through a process of "recognition" of knowing that comes out of Consciousness.
When we look at anything that seems outside the body or consider any imagined image or idea, what happens is that the mind focuses attention and the awareness, which is really the projection of focused Consciousness, extends to encompass the object, and the knowledge, to the extent that pre-judging is limited, flashes into the mind, like an intuition. Therefore, there is no knowledge or image outside of the source of consciousness in the body.
This is also so in relation to knowledge of the Self - single pervasive Consciousness. When we repeatedly try to understand and know that part of us that understands and knows, especially by reading or being told about the lives and words of the Saints, Sages and Saviors, who are the living expression of the Truth and who speaking continuously of their ever abiding experience as Consciousness Itself, realizable without the use of the mind and the senses, then That Self, which is our own Self, "hears" and "recollects" Itself, and in a flash discards the use of the mind's mechanism of attention.
With this comes an impalpable, totally unique and radical experience some call a "churning in the nadis," which is a deep sense of on the one side the mind of thoughts and images and related physical sensations being sucked inwards no longer outgoing, and on the other side of a pervasive penetration of radiance that feels like de-contraction, as though the cells and atoms of the body, previously gripped by the force of maintaining an identity to myriads of images and impressions chemically encoded and stored throughout the body, are being blown apart by a penetration of radiance of such deepening and expanding intensity that the images hold no more interest. With this comes the pulsation of "I" - no longer, "I - this" and "I - that" but "I as I." A soundless single pervasive reverberation of pure Being That "I AM."
The words "I am the Truth" and "I am the Light of the World" spoken by Christ mean simply what every Sage, Saint and Saviors have said that "I am Consciousness Itself" and the experience of Absolute Truth beyond opposites. These words mean something to the Self, which is Itself the experience of these words, but little to the inquiring mind, which through continued quest becomes pure, reflects its Source and vanishes.
The experience of abiding as Consciousness Itself is non-dual, as seeing happens within a field of consciousness in which the spatial images are no longer differentiated. They appear and manifest like the ebbing and flow of waves on the ocean, all without the use of the mind's power of attention. The sense is of timelessness, of the state having no cause, of being unconditioned by time and space, space-like.
At first there is the sense of seeing both the world of senses and ideas, while abiding transfixed in a state even beyond purity, but over time even the abatement of images begins to dissolve.
And the waking field of consciousness begins to awaken to the subconscious mind, meaning that even dreams begin to fade. This means that you experience the world in the same way that you experience dreams, where you recognize that the dream and the player or protagonist, yourself, in the dream are both created or manifested by you. In other words, as you awaken, to what the conscious mind has categorized as subconscious, within the "field" there is no sense of separateness. It's all "I" without the slightest vestige of a thought or movement of breath.
The use of the senses and mind to see fade even further.
There are any number of practices, which necessarily depend, as well, on the study of scripture, as a reference point to be able to somehow come out of the progressive state of amnesia that clouds us over.
When the mind is pure, i.e., the heart, the mind rises or projects out of from the what yogis call the Spiritual Heart (unrelated to the heart chakra), not the brain which is the reflected consciousness, then there is a sudden "hearing" Self recognition, and the knot that binds the mind and body idea to the sense of "I" is sundered.
Meditations of all kinds and the various yogas encompass the path of what can be called "withdrawal and dissolution" - technically, the path of Pratyahar.
Of the various yogas, probably the most effective exponent is the path of Raja Yoga, as outlined by Sage Patenjali, and in the related commentaries of Vivekananda. In practice the basic components include fasting, to eat little or no food for the duration of the intensity of the practice, then 2 times a day, e.g., at 10 am and 3 pm to do a series of asanas very slowly watching every breath and the motion, while watching through the body, the mind in complete abeyance of any thought, so that the movement and breath are like a prayer or offering to God. Then 4 times a day a series of pranayamas at 6 am, noon, 6 pm, 11 pm for 1.5 to 2 hours at a sitting, while watching the movement of prana through certain main nadis. In the interim times you read non-dual scripture. As the weeks and months pass, you begin to become light, feel transparent, feel the still silent pervasiveness of the "I" and you come to be able to see as Consciousness without the use of the mind and senses.
Eventually in the stillness, something deep emerges - awakens, a force of discernment, of Intelligence, the sense of "I" independent of the notion of identity in reference to objects, a state often called non-objective awareness. This also comes about due to the mind no longer being used to generate thoughts, meaning that prana begins to accumulate throughout the body as a kind of kinetic or potential energy, which begins to take on an electromagnetic quality. Then suddenly it's as though a graviton in the Heart has been triggered and the mind is gripped by the pulsation of "I" and whole body fills with light (to paraphrase Christ's explanation of the experience from Luke 11:34).
The nadis irradiant act like a light in the darkness, meaning that you experience the ability to see as Consciousness, without the use of the mind or the senses.
All the abstract and poetic phrases we read in scripture are all describing just this. There is also another yoga, in which the practice of Pratyahar is one aspect, the other more predominant aspect being the practice of Radiance and Will.
Radiance, which in other meditation and yoga practices oriented to Pratyahar, comes much later, has 2 aspects: Many varied postures and movements combined with powerful breathing techniques, where the postures and movements put an expanding or contracting pressure in certain areas or systems of the body causing the blood to saturate there. Combined with the breathing, the purified and electrified blood then saturates these areas, removing impurities and filling the areas with voltage, life force.
Then in the passive phase of the exercise or kriya, the glands secrete to support the voltage in that area, which then balances throughout the body. The experience is one of pervasive deepening "radiance." In this yoga this balanced practice of Laya and Pratyahar is called the Yoga of Light, because through it all the nadis and the entire body field are illumined within the body field.
Once the body is so charged, it becomes capable of amplifying sound, which means that certain types of mantra felt reverberating powerfully throughout the body field, whether repetitive mantra, as with kirtan, or specialized laya mantra combining breath, bhandas and cadence, balance yet increase the voltage geometrically.
Systematically, in hundreds and thousands of yoga sets and kriyas of many varied types, and mantras, the electro-chemical encoding of impressions and images throughout the body are dissolved in the force of radiance, a balanced flow of voltage / life-force that vibrates above the frequency of thought.
The radiance continues to extend and deepen until one begins to feel the sensation of penetrating de-contraction.
The mind's mechanism of attention, which typically focuses energy-consciousness in the body and to illumine the encoded thought impressions, is gradually overcome by the rising voltage that becomes greater than the voltage of the attention mechanism. This means that you begin to notice that thoughts are in abatement and you experience yourself as spatial consciousness. You feel the entire body radiating and dissolving without focus or attention - at once!
As the nadis brighten, the ability to see spatially without the mind begins to encompass the area around the body, i.e., the entire body field. In this yoga practice, this is called the "neutral mind" state or satvic state.
You experience yourself as spatial consciousness. Gradually, as the sense of de-contraction continues, giving a deepening sense of penetrating light that blows apart the atoms and cells of the body, various layers pure mind begin to unfold giving the feeling of pervasive Goodness, without its opposite, a sense of devotion and quest for the Truth - in a steady emergence from the previous cloud of amnesia.
Then there arises the beginning of a sense of a force of singular Intelligence that irradiates through the body and mind with a force of enquiry as to the source of the seer.
What is happening is that you, as an individual unit of consciousness, begin to "impact" the Infinite all-pervasive Consciousness which is the True source of the Light that, piercing through the Heart, illumines the body and mind. In other words, your voltage and vibration begins to come into the range of the Light Force that animates the Universe in all its dimensions with the Light of Being.
Suddenly, with the slightest provocation of words expressing the Truth, there arises a sense of intense "hearing." Recollection, as though coming out of a coma, a stupor or progressive amnesia. The entire field of consciousness is sucked inwards into the Heart and blasted out the other side of the shroud, and the body and mind stand Transfigured. Radiant like a Sun. The "I" pulses as "I" and even the field of consciousness begins to dissolve, and with it all latent images and impressions.
Your first words, if spoken at all are, like Christ, Nanak and Krishna and everyone that comes by this experience are: "I am the Truth" - "Sat Nam" - "Tatvamasi"
In this yoga, this entire practice is called "One Star Spirituality."
This is a practice, some elements of which one sees in Tibetan Yoga, which was taught at different times throughout the ages, usually in secret to special classes of "worthy" people, then lost. We read about it almost like a mythology of the Maha Siddhas of the past, such as Naropa, Tripola of southern India, the teachings totally destroyed, but not after being transported and translated by Marpa to Tibet and taught to Milarepa in recent time of 1,000 years ago.
Out of the distant past, this teaching suddenly comes on the scene again, as though warped in from another time and brought forth in a relentless revelation over a period of 35 years to provide a "practical" "applicable" means through which to open the dawning of a new Age, an Age no longer mired by endless discussions and considerations and comparing and categorizing of Truth, rather an Age in which one can practically apply a teaching that results in actually experiencing and living the Truth expressed as possible for everyone by the Sages, Saints and Saviors over the last 10,000 years.
The Teacher of this possible experience is Yogi Bhajan; the practical practice is Kundalini Yoga, a Yoga for the experience of the Totality of Being. Throughout his teaching period he reproved any that would listen to him and take his teachings to heart to believe in and pursue the experience and to stop at nothing short of That.