Let us add a few more thoughts on the ones already posted.One must first answer the question: concentrate on what? Since you can only concentrate (keep in consciousness immobile) on a few items, this is the most important question to be answered. It defines the aim of your practice. You may decide that you are going to concentrate on the correct fingering. That is your aim for the moment. So you put all your attention into getting the right finger on the right note. ..... (just to shorten)As soon as the fingering is correctly programmed in the unconscious, let your automatic pilot deal with it, and put your conscious attention on another component, say, the correct notes at the correct time.