[Coach]

Here's a drill that works for me:
"The Rectangle"
With your golf ball in position on the ground, take six tees, place two tees (or masking tape if hitting off a mat) -- one 3 inches above the ball (away from your body) and one 3 inches below the ball(nearer your body). Extend an imaginary line 12 inches behind the ball (parallel to your target line) from both 'center' tees, and place two more tees to form one side of the rectangle. Do the same imaginery line ahead of the 'center' tees. This completes your 2' x 6" rectangle.
Now, placing a ball between the center tees, take a 7 iron and swing so that the club head enters the rectangle from the lower right corner, strikes the ball, and exits from the upper left hand corner. Use short swings first and graduate to full swings. When you perfect the 7 iron, move to longer and shorter clubs -- using the same inside swing path.
For me this was a better way to instantly visualize my swing path from the inside. This smaller frame of reference lets me focus on and hit the ball while easily seeing the rectangle entrance and exit points with my peripheral vision. I do not have to look too far ahead or behind for my points of reference. This drill has helped me two ways -- first teaching me to come from inside and second, improved my ball striking.
"Try it you'll like it."
Let me know if it works for you.
Coach