Saw Buck Showalter demonstrate this on BB 2nite a couple years ago - so simple that it made sense.
Re: Footwork/steps on routine GB to left side:
fielder steps directly to the target [1B] with his left foot [big assumption: fielder is RH

]. This establishes proper momemtum/body direction; he then replaces that foot with his right foot, as the left foot steps, again, to the target. This gets everything moving TO THE TARGET. Left foot points along the line to the target, right foot is closer to perpendicular to the line.
Arm angles, etc is too technical for me - this is very simple footwork for routine GBs. We had a 3B that always moved towards 2B as he threw towards 1B, then proceeded to airmail 1B...this helped him out a lot.