I encourage the students, well require is a better word, to have a lot of descriptive writing and figurative language in their piece. As a pre-writing activity, a week before we start the paper, I have the students bring an object to class. I don't tell them anything about it, except that they need to bring an object to class. We then participate in a descriptive writing session for 15 minutes.
The honors classes don't need too much in the way of "prompting", but for my college prep class, I created this poster to help them get started.
Any other tips for descriptive writing?