Many years ago a German teacher of English said to me, ‘I was trained to feel that I was responsible for all of my students’ mistakes.’ What a burden she was carrying!
Thankfully most teachers regard the process of teaching and learning as much more dynamic. My approach is to try to engage learners so that learning becomes a discovery. Of course it’s not always possible to make everything fun fun fun but it is possible to stimulate learners so that they feel they want to learn.
Teaching needs to be flexible so you can adapt to what your students need. If you are forced to use less-than-wonderful course books you will probably need to use a good helping of additional material. Quite often it is possible to negotiate the course with your students. Once your have their buy-in, motivation can often be much higher.
For learners who are already highly motivated you can help them understand the best way for them to progress by identifying priorities, working on their study skills and helping them become independent learners. Naturally you will also need to select or recommend appropriate materials and provide lessons that push them to the next level.
More advanced learners will need help maintaining their level and gaining deeper insights into English.