I am a big supporter of teacher development. That includes teachers being developed by their superiors and colleagues but also teachers developing themselves. In fact, you can’t have one without the other.
One good way to develop is to do peer observations. You can find some good guidelines and suggestions on the site from the university of Minnesota. These are very useful for corporate Business English trainers as we often have a bit more freedom and need to adapt to each client so we need to develop ourselves to meet every client’s linguistic needs, learning style and rhythm.