The Canadian Association of University Teachers has written a comprehensive Teaching Dossier Guide. It was first prepared in 1986, and the most recent update from 2006.
The Guide (download the pdf here) contains a general explanation of what Teaching Dossiers (or portfolios) are, and how it can be used in academia, how to create a dossier (and what to include), and also contains an example dossier.
The focus is on the use of a teaching dossier as part of an evaluation process, and so it stresses evidence, clarity and conciseness. This is a good resource if the purpose of your dossier is for employment or tenure for example.