Being an ESL teacher can seem daunting and impossible for someone who has little or no experience in this field. Most newcomers believe a teaching degree is required to be an effective teacher. This is not true. While I would argue that a TESOL teaching certificate course will provide the training, what makes a good ESL teacher is a combination of several things.
First and foremost, the teacher will have a native or near-native grasp on the English language. As you will be giving information, answering questions, and correcting mistakes, it is important for the teacher to demonstrate a knowledge of the different language systems. This doesn't mean that you have to know the name of every grammar term. You should, however, be able to explain language concepts in terms your students can understand. After all, you don't want to have to resort to explaining something with "English is strange like that"; or "That's just the way it is." Remarks like this will leave your students frustrated and their confidence in you severely eroded.
Just because a teacher is a native or near-native speaker doesn't mean she will automatically be a great ESL teacher. Other qualities must be found if she is to make an impact on her students.
ESL students are typically quite nervous about their English skills and lack the confidence to use them. Although many of them have previous English studies and knowledge or currently use English for work or other activities, students tend to lack confidence that they can communicate in English. A good ESL teacher, then, must have the ability to encourage and build confidence in his students. Giving encouragement, praise and showing the willingness to point out areas of improvement are hallmarks of an effective teacher.
An ESL teacher also must have a bit of a creative streak. Most ESL students, especially those who are older, are not interested in spending hours pouring over grammar exercises and documents. Studies have shown, and my own teaching and learning experience has confirmed, that this is not the best way to learn a language. A language is best learned through use--that is, speaking about many things in many different situations. Therefore, a good ESL teacher must be able to think of creative methods for teaching and learning. Some ideas might include reading and discussing articles of interest to the student, practicing role-plays, or performing actual activities using English.
A good ESL teacher knows that he is not to do the majority of talking. Instead, he quickly assesses what makes each student tick and how each student responds and then begins to ask many open-ended questions. The goal of the ESL teacher is to get the student to speak and express in whatever way possible. A student who does not speak cannot make mistakes, be corrected, or improve. A good ESL teacher draws the student out into a place of being able to express willingly and, later on, confidently.
In the end, anyone who truly has the desire to help others learn, as well as a basic knowledge of the language and teaching fundamentals, can be an effective English teacher.