My experience: posture matters - for example sitting on a pillow is not good enough, I learned I need to sit on the ground with the pillow under my tailbone, my lower back is straighter that way. Recommend going to a Zen center, they teach posture really well. Also esp. how the Mokusho Zen guys do it, facing a white wall and looking 45 degree down, it works better for me than closed eyes or open and looking around.