MR meisjohn
There has been much discussion on this topic in the past ... performing a search will yield many answers.
To close, when photofocusing, use a 'soft and relaxed gaze' and try to see the whitespace, imagine an X connecting all four corners or see beyond the book as though using Xray vision.
In time, the Photofocus will become automatic. I've gotten into trouble because I have a tendancy to go into Photofocus at will and I look spaced out. My wife takes it as though I'm not listening ... which is far from the truth! 
