1. The mode of a data set is the value that appears most frequently. 2. To find the mode, list all values and count how many times each occurs. 3. The value with the highest frequency is the mode. 4. If no value repeats, the data set has no mode. 5. If multiple values tie for highest frequency, the data set is multimodal and all such values are modes. 6. Example: For data set $\{2, 3, 3, 5, 7\}$, the mode is $3$ because it appears twice, more than any other number.