As a power amplifier is tuned, what reading on its grid current meter indicates the best neutralization?

When a power amplifier is properly neutralized, the input and output circuits are isolated from each other regarding RF feedback. Therefore, tuning the output (plate) circuit should not significantly affect the input (grid) circuit. If tuning the output causes a large fluctuation in grid current, it means RF energy is leaking back from the output to the input, indicating poor neutralization. Thus, the best neutralization is achieved when there is a minimum change in grid current while adjusting the output circuit. Distractors suggesting a search for maximum or minimum absolute grid current are incorrect because neutralization is about isolation, which is measured by observing the interaction (or lack thereof) between the output and input tuning.