A post from last week on ProfHacker reminds us that it's time to conduct mid-semester course assessments--those formative check-ups that tell us how we're doing in time to make adjustments to our courses. The timing of that post coincided with a workshop sponsored by the Center for Faculty Development that presented numerous options for framing midterm assessment instruments, including the thoroughly tested and widely applicable "College and University Classroom Environment Inventory." Maryellen Weimer has written about this instrument here, and it is available for the asking if you email the Center for Faculty Development.
A simpler approach suggested in the ProfHacker post is to ask your students to write responses to these questions: What's going well? What needs improvement? What can the students do to improve the class? What can the instructor do to improve the class?
Even a simple approach like this that takes no more than 10 or 15 minutes of class time can convey to students that you care about their learning while providing you with some rich feedback useful for teaching improvement.