Key insights
- Start every bar chart's y-axis at zero. Truncating the baseline turns a +4% change into a fake +400% explosion — the single most common way charts mislead.
- Match the chart to the question. Bars compare values, lines show change over time, and pie charts fall apart past ~5 slices. The question picks the form, not your taste.
- Aspect ratio rewrites the trend. The same rising series looks flat when squished and like a spike when stretched — balance it so the average slope sits near 45° and reads honestly.
- Maximize the data-ink ratio. Strip gridlines, drop shadows, 3D skew, and boxed legends, then label the line directly. Every remaining pixel should carry data.
- Color is encoding, not decoration. Use one hero color to spotlight the series that matters, and choose categorical, sequential, or diverging scales to fit the data type.
- Title the chart with the takeaway, not the metric. "Revenue flat since March" tells the story; "Quarterly revenue" makes the reader hunt for it.
Do / Don't
- Do: Start every bar chart's y-axis at zero, no exceptions.
- Do: Pick the chart type from the question you're answering.
- Do: Spotlight the one series that matters with a single accent color.
- Don't: Truncate or crop an axis to exaggerate small differences.
- Don't: Add gridlines, shadows, or 3D effects that encode no data.
- Don't: Reach for a pie chart when you have more than five slices.
