a. Practice the most difficult exercise or piece first while you are fresh. You will never accomplish the tasks you dread if you always put them off.
b. Building time is where decisions of fingering and pedaling should occur. Make whatever marks in your music that are needed to play them the same way each time, but not so many that the page becomes confusing to read.
c. Use building time for vertical dissection--never play through an entire piece at this stage. Go immediately to a short section that is difficult for you and turn it into a drill until you master it. Perfect-measure practice, especially starting at the end, is very appropriate during building time.