This is part of what I have to cover in my OSSLT (literacy) course.
It walks them through how to write a descriptive paragraph.
Before teaching this, I often read them passages from Harry Potter because she writes FANTASTIC descriptions of everything - covering all the 5 senses.
The kids really see the power of imagery.
-a descriptive paragraph explanation (what it is)
-practice with similes
-an outline (second page with boxes)
-space for them to write their first draft (I make them type it)