How do you approach a piece for the first time?
I am a lousy sight-reader. I learn pieces by heart before I ever touch the piano. When I physically practice a piece on the piano, the only thing I do is search for the right intonation, the right atmosphere, etc. Of course, separate hands may be involved, like a conductor working only with a group of the orchestra. Sometimes, when aural feedback distracts me (yes, this *can* hold you back, although it may sound like musical/pedagocial heresy), I practice the piece on a dumb keyboard. This is not as mechanical as it may seem; it requires lots of concentration - hearing the intonation in your head and moving accordingly. Sometimes I do the reverse: eyes closed and only fingertips + ears active.
Paul