The DEEP DIVE
There is no prerequisites of any kind, and no goals, except one - to reach complete and absolute inner stillness. No touching any other subjects, like chakras, ethereal vibrations and energies etc. From this point on, everything else, everything we know, should be considered as distractions, external/internal noise we are trying to get rid of. No books to read, or lectures to listen.
There is one little requirement of commitment. Because it's gonna take time and effort, some might get there in few weeks, others in few years but whatever end of the spectrum any single individual is at, each and every should assume it will take a lot of time. And for various reasons, but mainly because the state we are trying to achieve is not natural, normal state of operation for our minds, brains, on the physical level, and there will be changes on physical level in our brain pathways if we chose to continue.
Have you ever noticed we tend to learn something better and easier if we practice something for 20-30 minutes at a time, but daily, for few weeks or months, rather than trying to just get to our goal in one go, grinding 12-15h hours every day with do or die attitude? Overstressed minds start to fight back, and it's not very helpful, most of the time. We gonna exploit that feature. Doesn't mean that way it's gonna be very easy, but because it's hard already as it is and we should take advantage of the natural processes where possible.
We start with daily meditations, short ones, if we can spare only 20 minutes, that is great, but even 5 minutes almost as fine. But the key is consistency, the daily commitment. We don't need to commit how much time we dedicate to practice, but we must commit to the regularity, the daily frequency of the practice, the latter part is orders of magnitude more important than the first part.
The environment? Time of the day? Not important. Preferably varied. At home alone, on public transport, sitting a waiting room for some appointment - all and every place location were you are able shut your eye lids for few minutes - is a perfect time and place for your daily practice.
Does music, binaural beats helps? No, not really, here it's all a distraction. For one, we try to get rid all and every noise, and everything is considered noise, so adding some music to it, just adds noise. And second thing, we don't just try to get rid of mental noise, but emotional noise too. Music tend invoke and provoke emotions, feelings. So if you want to make things harder, want some extra challenge, then sure go ahead. Otherwise it's not very helpful, in this specific practice (there may be some uses in other kinds of practices though).
So got your eyes closed? Good. Let's start diving through all the stages of silence.
At this first step we can actually use some more traditional, better known methods to quickly achieve deeper level of relaxation. Like focusing on breathing etc. First we are only distancing from external noise, visual, audio, tactile, all the sensory noise our "spaceships" get bombarded by constantly. Which can be challenging in it self, but many people naturally good at it, just look at all the daydreamers, they can be complete out there somewhere even at work, or some minds just shut off even mid conversation. So it's very achievable on demand.
So couple minutes in and we completely ignore the outside world. Now comes the hard part - shutting down the inner noise. The not thinking, not dreaming, not feeling anything. If it's sounds hard, or even impossible, it actually is hard, but not impossible, it's a little unnatural, our brains are not designed to operate that way, they don't like to operate that way, and they are simply not trained and not used to operate that way. But it's perfectly OK to struggle, just like it's perfectly OK to struggle at first when trying learn riding bicycle, or learning to swim. To greater or lesser extent, meditation is as physical skill as any other, which we actually can learn only by trying and trying and trying, and not from books and pictures. Only need to know it can be done and to commit to achieving it.
If after few days or a week you manage to achieve that place/state of completely inner silence/stillness, even just for few seconds, before starting to daydream or falling asleep, it's still a great achievement. From there we just need to practice to stay there for longer and longer and feel comfortable having no thoughts, no desires, no feelings (very important) in completely darkness - to feel comfortable having nothing, feeling nothing, being nothing, suspended in nothingness, floating in the void.
When (not if) in some weeks or months you are finally there, where you can actually achieve that state at will, inner state of being nothing but a faint speck of light suspended in pitch black void, with no feelings, emotions, thoughts, fears and desires - congratulations, you achieved supremacy over your machinery! You now gained tool capable of unlocking all kinds of things, AP/OBE is only one of many possibilities. But that would require entire new chapter probably.