When my reader and I come upon a plot, I always start by having them define the x and y axes, and then I have them trace the general shape of the lines on the back of my hand, starting in the bottom left corner of the plot. From here, I ask if there are any patterns or distinctive features. I ask if there is a maximum, if there is a minimum, if the lines form a curved shape or a parabola.
There have been cases where I missed something critical in a plot because the reader did not describe it to me. When this happens, it is not their fault but mine. It is my responsibility to get better at knowing which questions to ask to extract the information I need.