Students (especially at high school or lower college levels) often have
a hard time deciding which variable to plot along the bottom of a graph.
A very simple memory aid suddenly occurred to me today -- "looking up"
the answer on the graph.
If I know the volume of water and want to find the mass, I would plot
the volume along the bottom and literally "look up" the mass by tracing
upward from the volume to the line representing the mass.
If I do some experiments to determine speed as a function of distance
fallen, then I would plot the distance fallen along the bottom so I can
"look up" the result later.
This seems a very easy way to get students to decide how to plot their
results. Maybe it is an old idea, but I certainly don't recall ever
hearing it before.