Research has shown that the more detailed a writing assignment is, the better the student papers are in response to that assignment.
Instructors can use that tendency to help students write more effective papers.
Writing assignments are much more valuable if they can be part of a process of development, not merely an end result. Try to design a sequence of writing assignments that will enable the students to apply what they learn in the early stages to the work they do in the later stages. This step guarantees that students will not write the whole paper in one sitting and also gives students more time to let their ideas develop. This check might be something as informal as having students work on their prewriting or draft for a few minutes at the end of class. Or it might be something more formal such as collecting the prewriting and giving a few suggestions and comments.