It's important to think about the story you're trying to tell with the data and choose the visualization that communicates that story most effectively.
Avoid using a pie chart when the data you're presenting isn't naturally part of a whole (i.e., it doesn't add up to 100%).
Use 5 or fewer discrete categories that add up to 100%. Limit the number of slices to 5-7 to avoid clutter and make the chart easier to read.
Try to avoid using a pie chart when the distinctions between data points aren't large (24%, 25%, 25%, 26%, for example), as this can lead to misinterpretation.
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