Don’t try to teach English. At least for teenage and above who are past foundation level. Teach something interesting – art, history, simple science, geography, natural history, environmental issues, sport, etc. The English learning will happen along the way. The idea is to spark a lively discussion where the students are the ones asking the questions and the teacher a source of answers. This forces the student to actually use the language rather than just learn vocabulary and grammar rules by rote.