How do you know which measure of central tendency best describes the data?

The answer will depend on the nature of the data.

• If the data are qualitative then the only option is the mode.
• If they are ordinal then you have a choice between the mode and median. The mode may be a better measure when the data are very skewed. Otherwise the median is usually better.
  
• For any higher level of measurement is is also possible to calculate the mean. In such cases the median or mean are better. For very skew distributions the median is better but otherwise is should be the mean.