One of the most challenging experiences in my career was teaching English for Specific Purposes. I was teaching business English at the French University in Armenia to 1st and 2nd year majors in management and business studies. It was exactly then that I started reading ESP literature, since the courses I was teaching posed so many new questions. For instance, this was the first time I felt what it meant to challenge the teacher authority. Before this course I had felt quite competent teaching general English, because I was familiar with the most topics covered in GE textbooks. However, business and management were alien territories for me, and I had a hard time preparing for the lessons. Of course, I remembered very well that many authors writing about ESP recommended relying on students' knowledge of the specific discipline and thus yielding the domain of expertise to them. However, I was quite hesitant to follow this recommendation, because a part of teaching undergraduates in Armenia (well, this is true perhaps anywhere) is to make sure your students do not doubt your knowledge. Otherwise, except the de-motivation and the disrespect, you end up with a hell of a classroom: girls chatting non-stop or texting on their mobiles, boys becoming as unruly as walking in the classroom, commenting everything and everybody except their studies and what not (of course, this is an extreme scenario, but unfortunately, not very unrealistic). There still can be some classroom management and behaviour issues, but this is increasingly less so, if the students trust the expertise of their teacher.
So, to prepare for my first lessons meant at least four hours of painstaking reading of economics textbooks and occasional phone calls to my friends who had studied economics:-) I believed that the mastery of the content was essential for the ESP teacher to conduct a meaningful lesson (and I still do, though my opinion has changed considerably). Once I felt that I had established a good rapport with my students I felt less embarrassed to confess my ignorance of the content they knew quite well:-) Though I still prepared a lot for each lesson, I felt more comfortable to engage in a learning process myself with the help of the students. I think part of the reason why we both benefited from this process was my open statement that I needed their help. I still can remember the smile on the faces of some of them. They obviously could not hide their happiness for being appreciated and being treated as knowledgeable adults who are trusted by someone who they thought should have all the available expertise:-)
This was a difficult shift for me, but one I never regretted. What helped us to make the change was our openness and the negotiation over the change of the practice in the classroom. Had we been unable to negotiate, to make certain concessions, (e.g. both of us had to challenge our stereotypes about teaching and learning; I had to learn their content, they had to learn mine, etc.) we would have failed the learning process. I wouldn't have been able to teach the language, because I couldn't understand the content and thus couldn't design meaningful activities, and they wouldn't have learnt much, because such restricted instruction would not have addressed their learning needs.
However, I understood that this cannot always be the case. Sometimes, as in real life, some parties refuse to negotiate and then all end up in the least effective process of learning. I still think though that giving it a try is worth the effort. My experience of teaching ESP has shaped my own approach to it which I can summarize as the following:
I think at least some essential knowledge of the content is necessary. I don't agree with those who put the whole responsibility on students (what if some students don't know the content enough to help you? When you do know the content, you provide them with another chance to master their major as well) So, when you decide to teach ESP, you should be clear that your workload will double.
Negotiation over the learning process is a key to effective learning. Don't consider this a waste of time and effort, it definitely pays off!
Your students can be facilitators in the learning process, but you are the one who guides it. You are the one still responsible for designing learning activities. This may seem a truism redundant to be repeated, but unfortunately, some teachers fall into the trap of false student autonomy in the result of which not much learning takes place. Yes, students may remember such teachers as quite nice people, the lessons as quite entertaining and fun, but when it comes to what they have learnt, they 'forget' to mention anything!
Now, I anticipate quite emotional disagreements with this:-)