One area of character description that novice writers often overlook is physical gestures. That can be problematic.
For example, many novice writers will tell a characters’ emotional state rather than show it. Describing a character’s physical gestures and body movements, however, allows the reader to infer that emotional state while adding a level of detail to the text that helps the reader better imagine the scene and so become more engaged in the story. So rather than writing They grew sad upon hearing the news, instead show their sadness with Tears welled in their eyes at the news.
When doing this, selecting just the right physical detail is vital. After all, varying degrees of a general physical gesture infer quite different emotional states. For instance, if something humorous is said, a chuckle shows a stronger response than a grin but less of a response that an all-out laugh.
In addition, the description of the physical gesture must be balanced against its importance in the the rest of the story. You can’t be too spare in description but can’t be too long-winded, either. Learning exactly what is appropriate is a matter of mastering the craft of writing.
Finally, you’ll have to be consistent with the details. Two jokes of equal humor should generate the same response each time from a character. With a little creativity on the writer’s part, this physical tic even can be a marker that becomes associated with a specific character; consider that whenever Mr. Spock of Star Trek fame finds something interesting, he raises an eyebrow.