I found this MO question while writing my own teaching statement. I'd like to point out that the Notices of the AMS published a survey which identified quite a few themes in successful teaching statements. I will paraphrase the list, beginning with the most-cited comments:
- Specific examples linking philosophy to practice.
- Dedication to teaching.
- Good writing.
- Thoughtful reflection on teaching.
- Student-centered.
- Match between individual and department.
Here's a handy rubric from the University of Michigan, also informed by a survey.