For zazen, you will need a quiet room. Eat and drink in moderation. Forget about the concerns of the day and leave such matters alone.
Do not judge things as good or evil, and cease such distinctions as "is" and "is not." Halt the flow of the mind, and cease conceptualizing,
thinking and observing. Don't sit in order to become a Buddha (enlightened), because becoming a Buddha has nothing to do with such things
as sitting or lying down.
in the room that you use for zazen, spread some thick mats and place a firm, round pillow on them. Sit on the pillow with your legs crossed either in the full-lotus position or in the half-lotus position. This means [in the full-lotus position] that you place your right foot on your left thigh, and your left foot on your right thigh. In the half-lotus position, you just put your left foot on your right thigh [with the right foot on the mat beneath your left thigh].
Loosen your clothes and belt and arrange them neatly. Next, place your right hand [palm up] on top you your left foot, and place your left hand [palm up] in the palm of your right hand. Both thumb tips should touch lightly.
Now regulate your posture so you are sitting properly, leaning neither to the left nor to the right, forward nor backward. [Looked from the side], your ears and shoulders should be in a straight line, and from the front your nose will be in a direct line with your navel. Place your tongue against the roof of your mouth, and keep your teeth and lips closed. Your eyes should be [slightly] open, and your breathing should
be soft.
When your body posture is correct, breathe in and out [once deeply]. Sway left and right [several times] and then sit firmly and resolutely.
Think about the unthinkable. How do you think about the unthinkable? Non-thinking. These are the essentials of zazen.