10- I use mirror to keep the body perfectly upright as far as possible when viewed from the front.
11- My head, I noted, if left alone during meditation, tends to place itself in an upright position, sometimes inclining to to the left sometimes to the right, but never turning itself a little bit downward towards the ground, nor turning itself upward all the way towards the nape, but settling somewhere in between. By reviewing a video I recorded about myself while meditating, I noticed my head tends to lean towards the right more so than to the left. I corrected this posture.
12- There is also, I noted, a general tendency of mine: not to remain motionless but to move again and again especially when exciting or stressing thoughts arise.
13- I generally turn down the face a little bit and hold it there motionless, as the author recommends; this helps me still the body and by implication the mind; Of course, I do other things like breathing and stressing the lower abdomen to still the body and the mind.
14- I also draw the chin a little bit inward, as the author recommends it, but I have not noticed a difference.
15- I also stick out my forehead. This helps me counter a general tendency of mine: contracting the forehead as if I am shortsighted person attempting to see things from a distance.
16- The author recommends we extend these postures, waist forward and upright body position as far as possible, for instance, into our daily lives, so that they become the way we sit or, generally, the way we carry ourselves around. This is a great recommendation judging from my first hand experience in sitting on a chair implementing as far as possible the recommend postures.
Generally speaking, when I sit as recommended, I feel strong desire to move after a while and then I move. After movement, I re-start sitting again. In the previous times before I knew how to sit as recommended, I used to feel shoulder pain and other displeasures, which I did not know how to properly react to them.
17- Hand Positioning, I place the right hand under the left hand. I then let the thumbs touch each other at their tips, forming some sort of a whole. This is my favorite hand positioning for now. There was a time when I had another favorite hand positioning. I was still placing the right hand under the left hand. Now, instead of letting the thumbs touch each other at their tips, I let the right hand thumb touch the palm of the left hand.
18- There is also another method of hand positioning mentioned in the book. I have tried it but I did not find it as enticing as other methods just mentioned.
The hand positioning in meditation where thumbs touch, creates a certain feel of stabilizing pressure when meditation advances. This signals to me that the meditation has advanced.
See the link below to get the books: Zen Training: Methods and Philosophy, see for more on the chapter of posture.