One of the major skill sets of a great language teacher is the ability to "prompt" students so they will generate language. It isn't easy and with time a teacher becomes better at replying, prompting, leaving unfinished, their utterances so that students are put into a position of "having to communicate". It is a skill that even gets more refined as the teacher adapts and scaffolds at just the right level/language.
EFL Classroom 2.0 has so many online language generators that help teachers out in this regard. I've put together many that can with a click of a mouse, start students talking. Also, in ppt and paper/flashcard form. Here's a list - try them with student and I'm sure you'll see they work like a charm. The teacher just keeps circulating as students take turns in groups, answering the prompt.