This idea is great for independent practice or for work as a group. Start by chosing a well-known character. Cartoon characters are ideal. Then, without using that character's name, describe that character in the best detail possible.
If working in a group, make sure that each person chooses a different character (I suggest handing out cards with character names on them) so that participants can then go on to read their descriptions aloud.
Although some descriptions might obviously portray a certain character, it will help for each member to see how easily others can figure out the character, so that they know how well they are using descriptive writing.
I suggest this creative writing activity because not only is it a good way to practice, it is a fun activity that can be turned into a game.