What better way than to have the student pick a topic of choice, and write about it. Sometimes the instructor may give the student an idea to write about, but ultimately the instructor should guide the student into picking a topic of choice that pertains to the student's interest. Instructors can be very selfish when they ask students to write about a topic that doesn't interest the student.
Students have their own ideas in regards to writing topics.
Teachers should encourage students to pick a topic and write about it. It's stiffling to the student when students aren't given the freedom to become responsible writers.