Most bad charts are the result of picking a shape before naming the comparison. So name the comparison first, then draw the very same numbers seven different ways. Watch which encodings carry the point, which merely survive it, and which quietly destroy the only thing you were trying to show.
1 · Say the comparison out loud
There are only five comparisons you will make in ninety percent of professional documents.
2 · Draw it
The dot under each button turns green, amber or red once you have picked a comparison — but try the red ones. Seeing the failure is the lesson.
3 · Finish it
Four formatting moves that separate a chart that argues from a chart that just exists.
The chart
Pick a comparison to begin.
Waiting
Choose one of the five comparisons on the left, then a chart type.
Encoding hierarchy
How accurately people read each visual property. Put your most important quantity as high up this list as you can.
Build notes
Colour carries categories, not magnitudes. A five-line chart in five bright colours makes the reader consult a legend five times. Grey out everything except the one or two series you are actually discussing — this single move improves more charts than any other formatting change.