Again a complete dumbing down and oversimplification. Nei Dan requires both effort (setting of the conditions/causes) and no effort (the spontaneous arising of the effect/result). You won't get anywhere with no-effort - and you won't get far with only effort.
Then there is the same thing on a sort of holographic micro-scale where even within effort there is no effort... as a very basic example, you bend the knees not by 'doing the action' of bending the knees but by letting go anything that keeps your knees straight...
But this post isn't about the 'how'.
This is 'the great work' - and obviously I'm going to hugely oversimplify things - and leave out a ton of processes and nuances.
This is just to give an overview of alchemical practice from a traditional 'classical' perspective. This is how Nei Dan masters that have any real attainment do it.
To understand Nei Dan, I personally found it important to understand the difference between alchemy and other approaches.
Alchemy is an art of transformation. But people don't necessarily quite appreciate what transformation entails... or how literal it is... there's a world of difference between a caterpillar and a butterfly - they are fundamentally different (have a look at Silent Thunder's thread on the subject). That's the nature of transformation. Transformation is permanent. And it's a full transformation at every level of one's being - physical, energetic and spiritual.
Many other approaches - or at least the approaches that are available to people are more to do with experience... for instance, one is to experience pure non-subject-object consciousness then try to experience it for longer and longer. This might work in a monastic setting... and might be quite helpful in many ways... but it's fundamentally different to how Nei Dan works.
Alchemy works on the premise that everything - every physical 'thing' and every state of consciousness has an underlying energetic 'substance' to it. The alchemical method is gathering these substances and working with them in a specific way to achieve permanent transformation. It's a huge endeavour - just 'accessing' the primordial states of consciousness is beyond most people... let alone penetrating the state to touch on the substance behind it... and then having the capacity to bring this primordial substance back and condense it... It's not an easy task
Jing, Qi and Shen are the first substances one works with... These are replenished, regulated, and refined to a high level. This is the work of 'laying the foundation'. This is the stage where one transforms the functioning of one's body and consciousness to a very high level...
Yes - the various orbits will have opened... in fact all the channels will be fully open... Much of one's karmic seeds would have been 'burned away' through the foundational alchemical processes. One would have achieved and would be regularly swallowing the 'jade fluid' that floods the mouth from the upper dantien.
This is the stage where health and vitality are developed and revitalised to the state of a child. Which doesn't mean acting goofy and childish... it's replenishing jing and qi to the extent that one's body becomes more like a child's... I always admire how my friend's 2yr old can sit completely relaxed, yet fully upright with perfect posture... how he can seem so delicate, yet demonstrate so much strength and resilience... How his body has this layer of puffiness which is the overabundance of qi filling all the spaces in the soft tissues of the body... How he's able to learn incredibly complex things with no effort etc... This is what is meant by returning to a child-like state.
There's also specific training to develop correct mental qualities and levels of meditative absorption - like the various levels of samadhi and Jhanna in Buddhism. The various meditative practices (like Xin Zhai and Zuowang) would need to be at least close to mastery - so that one's heart-mind is completely still, and simply sitting and closing one's eyes you enter a samadhi state... even with eyes open one's mind should be largely quiet and still - no internal dialogue or unintended movement of mind. The difference between being asleep and awake is only very slight.
This is all just preparation - setting up the conditions for the development of the alchemical agents.
The Dan - the golden elixir pill is made of the condensed 'substances' of one's congenital, primordial nature... Often when people have an awakening, as their 'self' dissolves, they will see a very bright light... this is the light of the Yuan Shen... This experience in itself is quite transformational... Being able to stay in this light gives rise to various levels of direct insight... this is a similar state to the Jhanna absorption in Buddhist traditions... Some call this awakening... some call this enlightenment (it's not!).
What the alchemist has to do is enter this state until they are able to touch on the underlying substance of it... It's like plucking the pure essence of this state from the primordial and then bring it back and compressing it into a pearl...
This is one of the 'ingredients' of the elixir pill...
At a birds-eye view, internal alchemy uses the underlying substances of Xing, Ming and the 'original breath' - which is that which gives 'life' to you before you're physically born. These substances are brought together and fused into the elixir pill... (then after the pill is formed one gestates it to form the golden embryo - but that's another story )
Each stage can be many years worth of full-time disciplined practice in retreat. Very few people have managed to achieve this process. And yet I keep seeing 'weekend alchemy retreats' where people simply imagine coloured balls