How to Meditate
Edited from a talk by Roshi Kennedy, 2020:
The two foundations of sitting meditation are posture and breathing.
Proper sitting posture helps you feel more comfortable, more sturdy, and to pay attention more easily. It also improves circulation and prevents strain on your joints.
Sit up straight. Place the center of your body between the edge of the seat and your sitting bone. Keep the back of your head, your neck, and your whole spine in a neutral, straight line. Do not lower your head, do not raise your head up. The very top of your head goes to the ceiling. Tuck your chin, slightly close your lips, and place the tongue on the roof of your mouth.
Drop your shoulders and relax your arms. Place your hands anywhere that feels comfortable. A common choice is to place them on your lap, with both palms upward, the left on top of the right. You may close your eyes or slightly open your eyes, cast your eyes down in front of you. Be aware of what is in front of you, but do not pay attention to it.
It may be difficult for beginners to relax the body. After you settle down with proper posture, begin to relax your body, starting with the head, then the neck, the shoulders, the arms, the chest, the back, the hip, the legs, and so on. Spend some time on conscious relaxation, while breathing through your nose. Observe any tension in your body and let go of it.
Counting the breath
This step is helpful for beginners. It helps prevent your mind from wandering. Count the breaths: (inhale) as 1, (exhale) as 2 and so on up to 10. Then restart the count. You may also count the exhale instead of inhale. If you get distracted with thoughts, and lose the count, start with 1 again.
Following the breath
Once your mind is focused on the breathing, you may stop counting. Observe and pay attention to the breath. Notice and experience all the characteristics of the breath, such as length, speed, and pressure, and track each breath from beginning to end. If you get distracted by thoughts, gently return to the method.
Another great description of zen posture and breathing can be found in the first two sections of the book Zen Mind, Beginner Mind by Shunryu Suzuki.