Posture I believe is of the utmost importance. You say you sit toe-to-toe. I have been lead to believe you should sit in full or half-lotus (depending on your flexibility). Your eyes should remain open but not focused on any point rather to see through whatever is in front of you. Getting your posture right is not an easy task and you should practice perfecting your posture from when you're in zazen, to walking or sat watching the tv!
I recommend 'On Zen Practice' by H. Maezumi, B. Glassman.