I am able to assist with the general mechanics of physically holding the body, of mindful breathing, mudras and mantras, but when it comes down to subtle sensation and the dropping away of thought, each of us is on her own and I will not comment.
Because each of us is unique and must find our own way into the subtle mysteries of the practice. Surely there are markers of mastery, but those too, from the Soto perspective, can be misleading...as the Vow describes, "Delusions are endless...." And unless you are under the guidance of a meditation master who grants you dokusan, be aware of the potential for delusion.
Hell! Be aware even with a master's guidance!
To endeavor to practice you must know the origin of practice"
"What are words?"
"One, two, three, four, five."
"What is practice?"
"Nothing in the entire universe is hidden!"
cartoon by Brian Hoffert
Dogen Zenji, (1200-1253), asked one question over and over again: Why, if we are already enlightened beings as the Buddha says, must we practice in order to experience enlightenment?
"Both exoteric and esoteric Buddhism teach the primal Buddha-nature (or Dharma-nature) and the original self-awakening of all sentient beings. If this is the case, why have the buddhas of all ages had to awaken the longing for and seek enlightenment by engaging in ascetic practice?"
A Study of Dogen: His Philosophy and Religion, Masao Abe, Albany State University of New York Press, 1992
We practice because we are unaware that we are endowed with Buddha-nature, and when we sit in meditation, we are simply Buddha.
Indeed, nothing is hidden in the universe, we simply need to become aware, and in meditation we can be aware.
Stages of awareness can be pointed out to us, but the goal is not to become so obsessed with those stages that we miss our awareness itself! We stroll right by our Buddha nature time and time again, on our way to a coveted goal.
What happens when we drop the goal?
What happens when we stop searching for the street sign, or throw the map aside?
Where is the destination?
Where is the enlightenment goalpost?
Shikantaza, "just sitting", is not about acquisition or achievement. If we rest in the ground of our being and just sit, we will realize that we exist in buddha-nature as a fish exists in water.
We exist in Love together, and all the pointing out or direction or words! will never be this Love, they can only hint at this realization.
Try not to cling to the sensations that arise in sitting meditation--allow all to drop away: aversions and euphoria are the same thing, just another form of delusion, anger or greed. Release judgement of whatever rises while sitting, and simply rest in what is before you.
Don't muddy the water over and over again as it begins to still.
This is being awake.