The trigger finger should move back as parallel to the bore as possible when pressing the trigger. Here’s a little exercise I designed at the elite Rogers Shooting School to help our clients practice moving the finger correctly. It requires no equipment and gives biofeedback on your performance. It is also the safest form of dry practice, other than from quizzical looks by others.
For revolver shooters, this is a powerful learning exercise.
I enjoy wearing my NRA Certified Instructor cap when I’m teaching, even when it’s not an NRA class. 🙂