There are many good sources for what a teaching dossier is and what it is not. It is likely that EVERY institution has a webpage on teaching dossiers.
For example, the University of Waterloo has a good reference to teaching dossiers.
University of Toronto also has one we like.
And, we are not going to repeat all of that good stuff here.
The UofT notes provide good common sense recommendations for what not to include. It does not have details about ALL of your pedagogical knowledge and ALL of the courses you have ever taught. For the most part, it should be more like an executive summary, hitting the most important points. Target 2-3 points in each area to discuss and demonstrate the breadth; do not simply repeat the same point three times.
You want to demonstrate with a solid examples your breadth and depth of knowledge, your comprehension of pedagogy, your self-awareness, your abilility to apply the appropriate pedagogy, your ability to analyse and reflect on your teaching, your ability to evaluate your teaching (pros, cons), and your ability for synthesis. We think that a good way to do this is by taking two courses, one learning outcome from each and describing the pedagogy used to reach this goal; explaining your interpretation and justification for the decisions made and any evidence that exists that your decisions were appropriate and reasonable.
You want to demonstrate that you know how to use the methods. When to use them, when not to use them, how to introduce them, monitor their use. You want to show that you are aware of any assumptions, strengths or weaknesses of the methods you are using and perhaps even methods you could have used, but decided not to.
When including material such as a syllabus, assessments, or rubrics annotate and highlight any 'best practice' or 'improvement' activity that has taken place to indicate that you are aware of the best practice, generally agreed upon practices, that you use them, and know how to include them in your teaching.
If you have a buddy-system, mentoring situation, or take advantage of additional teaching workshops etc., you want to share this and provide evidence that you and the students benefited from this. If you help others, this should also be shared and if you can provide evidence that your assistance actually helped, that is great.
You can describe any peer reviews or processes you use to review the courses each year, how you do reviews and adjustments during the term, and how you do a post-review of the course at the end with TAs and others; that is, do you have a quality control process in place for your teaching?
As noted in the UofT suggestions, you do not need to note or discuss all of the methods you know, you use, and the buzzwords you can pull out of the hat. You want to be concise with careful choice of sentences and examples. Often one situation can demonstrate multiple points when chosen with discretion. For example, you can take a 'year-in-the-life-of-a-course' and quickly describe the review process, take one method as an example, discuss how the method was evolved, etc.
Remember that a teaching dossier is where you document your philosophy at the strategic, tactical, and operational levels. It is where you provide evidence of the same. In many cases, it is best to use one course (perhaps two) for examples throughout, to provide a coherent context for those using the dossier; rather than giving isolated examples from many courses.
We think that a dossier should start when you start being a TA, when you first participate in the teaching process. The dossier 'file' can act as a log and diary for you. What you learned when. Use this to reflect upon. Use it for great examples as your craft final dossiers.