Basic rules
Do
Compare category magnitudes on a common scale and start the value axis at zero when length encodes value.
State the unit and sort order and reserve enough room for category labels.
Make the zero baseline clear and show direction and signs for positive and negative values.
Don't
Do not truncate the baseline to exaggerate differences or vary bar thickness between categories.
Do not rely only on color to identify categories or overlap an excessive number of bars.
Do not describe negative bars only by magnitude or distinguish gains and losses only through color.