When I was starting out as a young apprentice, one of my proudest moments was when I mastered the art of fine-tuning a water closet. It wasn't the first thing I learned, but it was the first real technical part of plumbing I discovered.
I could line up the ball, set the lift wires and bend the rod to adjust the float like a pro. Of course, that makes it sound like I come from a bygone era. Balls and lift wires have been replaced with flappers. Manufacturers now provide a set screw for adjusting the float.