Think of it as an interview.
How can you show that you are a good teacher?
The students don’t know who you are. They assume some credibility because you are teaching their class, but they don’t know how far they can trust you. Let them know.
Create a shortened form of a resume (not a vita) on the board, an overhead, or on the computer. Give them your education, your teaching experience, and (especially if that is limited) any other relevant experience. This will let them know that you are an expert.
Why are you a good teacher for this class?
Tell them specifically why you are a good teacher of this topic. (If you aren’t, leave this part out.) For my comp students, I tell them that I have a PhD in rhetoric. For my literature students, I tell them I am a voracious reader and have studied a lot of literature.
Let them know some things you have in common.
If you are an alumni of the school, let them know.
If you can relate to them on difficulties in learning English (or any topic), let them know. I always tell my students that I don’t expect that everyone in this class will get As, though I think most of them can. I tell them that sometimes a C is the very best work the student can do and that, if that is true for them, they should be proud of it. Then I tell them about two Cs I made that I am very proud of (Genetics and Geometry). I do not tell them about the two Cs I am not proud of. They don’t need to know that. But I tell them how hard I had to work in the classes and how difficult it was for me. I tell them that I didn’t give up and that, in Genetics at least, I was one of only 9 students who finished the course out of 70 who started.
If you are taking classes while you are teaching, let them know. It’s good for them to know that this is a job for you and that your education continues.
Show your humanity.
Students like to know you are “real,” but they don’t want you to spend the whole class period all the time telling about your baby or your grandbaby or your tabby. I introduce my family when I tell my students about my experience as a homeschooling mother and then I say that both my sons are now in college. I don’t talk about them all the time, but I let them know that I am a person as well as a teacher.