1. Be active, open, happy, interactive, with quick reflexes.
One of the biggest things, especially at the kind of ESL jobs that teachers almost always begin in, is keeping students engaged and happy to be with you, especially for kids. I know in my case this took a while because I had to change my general character. I am an introvert. But even people like us can engage with others. We oftentimes have a lot of stuff bottled up. As long as we don’t have to teach all day long, an introvert can be just as effective as an extrovert because of this. But it takes a willingness to change and some practice.
When I am in the classroom, I am always moving around. It’s better to move with a purpose but failing that, just pacing to match the energy level you’re at or walking around the desks keeps students interested. It’s good to use body language when teaching, but try to make it have a purpose. Just waving your hands around without reason may just confuse students. Some kinds of body language are obvious: making a face to show an emotion or moving your hands up and down to show higher and lower. But you can also explain things by telling a story, talking as you act it out. Then, when you want to see if students can guess or remember something, do the action without saying it, ask who can say it.
Eye contact matters a surprising amount. If you’re speaking to one student, of course look in their eyes. But even when I’m talking to the class I don’t look at the board or above their heads, I look one student in the eyes a few seconds, then let my gaze move to another. Try to get everyone more or less equally. This will have a powerful unconscious effect on students. They will feel that you care about them, will stay more interested in the lesson, and be more emotionally invested in class. It will also have a positive effect on classroom discipline.