What are some common but easily avoidable graphical mistakes?

John Kastellec writes:

I was thinking about writing a short paper aimed at getting political scientists to not make some common but easily avoidable graphical mistakes. I’ve come up with the following list of such mistakes. I was just wondering if any others immediately came to mind?

– Label lines directly

– Make labels big enough to read

– Small multiples instead of spaghetti plots

– Avoid stacked barplots

– Make graphs completely readable in black-and-white

– Leverage time as clearly as possible by placing it on the x-axis.

That reminds me . . . I was just at a pharmacology conference. And everybody there—I mean everybody—used the rainbow color scheme for their graphs. Didn’t anyone send them the memo, that we don’t do rainbow anymore? I prefer either a unidirectional shading of colors, or a bidirectional shading as in figure 4 here, depending on context.