[esltiger]

Read journal articles and books about teaching and learning.
Read teacher narratives.
Attend professional conferences.
Establish a mentoring relationship.
Put together a teaching portfolio.
Learn another language.
Do action research.
Do self-observation.
Observe other teachers.
Keep a teacher journal.

One rather obvious way we can develop our teaching is to read professional books and journals on teaching and learning languages.
Another way to work on development of our teaching and ourselves as teachers is to attend professional conferences. These are good opportunities to hear what teachers in your own area are doing in their classrooms, and good opportunities to present your own techniques or action research. It is also possible to attend one of the worldwide affiliate conferences attached to International TESOL.
Another way to explore our teaching is through establishing a mentoring relationship with another teacher. Mentoring is sometimes thought of as a new approach to development for language teachers, but in fact, mentoring has a long history. The concept of mentoring has certainly changed from the days of a wise old sea captain giving guidance to Odysseus’s on, Telemachus. Today mentoring is “an interpersonal, ongoing, situated, supportive, and informative professional relationship between two (or more) individuals, one of whom (the mentor) has more experience in the profession, craft, or skill in question.
A teacher portfolio is another additional way to explore and develop our teaching. Some ESL and EFL teacher preparation programs ask graduating students to put together a portfolio so that these teachers reflect on what they have learned in the program and have a collection of work that can be included with job applications.
Another way to explore our teaching as language teachers is to learn another language. Some advantages are: First, we can better understand the challenges that the learners face. Second, we can gain more insight into understanding language. Third, by assuming the role or learner, we can gain insight into ways of teaching that seem to work and don’t work, at least within our language learning setting.
Another approach teachers use to explore teaching is action research, an approach that centers on problem posing. The cyclic process includes posing problems based on what goes on in the teacher’s classroom, within a school, or beyond; systematically working through the problem by creating and initiating a plan of action; reflecting on the degree to which the plan works; and then posing a new problem based on the awareness generated from previous inquiry.
Observation is another way to explore and develop our teaching, including observation of other teachers and self-observation. Talking with other teachers about the teaching we observe is also a way to explore new possibilities in our teaching, as is writing about teaching in a journal.

[Eric18]

That's a solid primer for both new and experienced teachers.

You might also look at YouTube videos on a topic that you have taught. This technique allows you to compare your own teaching style with other teachers, from around the world - and pick up tips for sharing material.

Just a thought. Use or lose.