Ultimately, you have to know how to teach English to foreign learners. There are different approaches to teaching learners of different levels, and all the more so if they are non-native English speakers. There are specific approaches that you have to do, and additional strategies that you need to learn. Some employers abroad even require their English instructors to have certificates in ESL and TOEFL, to make sure of their credibility as teachers of English to foreign students. Some employers may also require you to take an additional qualifying exam as part of their application process.
The sounds of English are very important and can easily escape the untrained ear so phonics should be covered in-depth with both listening and speaking. Some students may have already studied grammar and spelling but know little or nothing about how to distinguish certain sounds. Cover vowels, consonants, and blends so that your student will not be afraid to learn and speak new or difficult words. Also writing, spelling, and reading should be covered but speaking should be the main emphasis if your target is English conversation.
Try to keep your classes interesting, upbeat and fun. Also do not scold the student too much when they make a mistake or they will lose the enjoyment of the class.
Proper pronunciation is often overlooked in the language teaching field. English textbooks and instruction manuals barely touch on the subject.
Yet proper pronunciation is a major part of learning the English language! The number of words with similar sounds but utterly different meanings can cause much confusion if the correct pronunciation is not taught.