Four ways to get students to use critical thinking in their writing...

1) Label and define what you mean by critical thinking for students and for yourself

2) Make sure that critical thinking appears in your assignment

3) Include Critical Thinking as a part of your grading rubric. Show what it means to be critically thinking at each level of assessment. Provide short samples of what critical thinking looks like for the writing assignment, if possible.  Sample  Another Sample

4) Allow students to practice critical thinking in small ways
     In order to give students "low stakes" practice in using writing to think something through, try using Microthemes