Basic rules
Do
Show magnitude and change along an ordered axis, with a clear baseline for the filled area.
Label axis units and aggregation intervals and distinguish missing data from actual zero.
Stack series with the same unit and provide both total and individual values.
Don't
Do not connect unordered categories or let overlapping areas completely obscure another series.
Do not fill gaps without explanation and imply continuous observation.
Do not present the vertical position of an upper series as its value or mix negatives into a simple positive stack.