The drill one 430 path drill stops the right arm from straightening- allows the body to open and turn- and keeps the golfer pushing force into the ground through the feet and legs. It also sets up the drill three post impact that keeps pressuring the shaft to the finish.
Connection- Power- Force...How do they all tie in? 
The end of the club is hidden by the hands but here is a visual drill that can help the golfer see and feel where the shaft should align to create consistent strikes on the ball. 
How do consistent ballstrikers get the clubhead to enter the ground at the precise point that allows pure contact. Watch and learn.
The golf club only stays on the target line for a short amount of time. It does however need to enter and exit in a manner that will spit the ball out straight and eliminate curvature. Here is a visual to how it works.
Shaft lean is one of the most discussed aspects of gaining a better strike on the ball. But what is it really? And how is it achieved?