Tips for More Readable Graphs

Over at Andrew Gelman's blog, John Kastellec (Princeton--Poli Sci) ignited a discussion (here) about "common but easily avoidable graphical mistakes" that hinder graphs' readability. While some suggestions are obvious, others are not. As well, the comments to John's post are as important and helpful as the post itself. When all is said and done, however, for my money the most important contribution to this topic remains Tufte's classic: The Visual Display of Quantitative Information (2nd ed.).