Evaluating Captions

To create a descriptive caption, think of the main focus of the picture and compare it to something else. For example, this cat appears to be sleeping, thinking, or resting in one spot. So what is something very still? Aha! A rock! The cat is still like a rock.
Therefore, this cat can be compared to the stillness of a rock to help the reader better visualize how still, or calm, the cat is sitting in the image.