When I was about to start teaching for the first time, some thirty years ago, I asked myself this very question and came up with the following answers:
Teaching is a collaborative process and my job is to involve my students in their learning and adapt as closely as possible to their needs.
I should be able to explain a language point in three different ways (assuming my students struggle to understand it).
Reviewing how I teach and the material I use on a regular basis is key.
I had no formal training and was about to teach English to French post-graduate law students. Needless to say the prospect was a bit daunting, but exciting as well. I had a chance to approach language learning in a radically different way from school. I used films, tv shows, games, humour, and a huge amount of energy to get my students to see that a language is a living thing and that speaking a language can actually be fun.
By the end of the first year, I looked at my notes and rewrote every single one of them! And if you speak to teachers, any teacher, they will tell you the same thing. We regularly review our lesson plans and tools, always aiming for precision, clarity, and maximum engagement on the part of students.
When I went back to teaching after working in publishing and running an independent publishing company, I started my classes from scratch. I had years of experience managing projects and people, better tools at my disposal thanks to technology and the Internet, but my approach remained the same.
What makes a good language teacher, is a question I still ask myself on a regular basis. Or more accurately, what I can do to adapt my teaching as closely as possible to my students' needs.
The key to any teaching, and especially language teaching is flexibility. A language is not a theoretical subject and students learn as they speak, as much as when practising listening, reading, or writing. This means that I rarely follow my lesson plan, because it's more important that my students speak and for me to be able to address any of their questions or doubts.
More than anything else, a language teacher needs to understand the psychology of their students in order to help them overcome any fear, anxiety, or self-criticism, which prevent them from speaking. To that end, the classroom, be it virtual or real, must be a safe space where they can experiment with the language without any judgement nor evaluation.
Finally, a language teacher needs to have a sense of humour, if anything to remind students not too take themselves nor the language learning process too seriously!
Don't hesitate to send me your questions.