In your opinion as a teacher, what's the ideal way to teach in class?

I would suggest getting them to use it as much as possible by introducing topics that they have a lot to say about. Be careful that you don't touch on a subject that is politically sensitive, but you can show a clip of a wildly ridiculous talk show from America and ask them to discuss what is wrong with it or if it would be popular in the China, for example. Getting them in a situation where they want to express their ideas but are out of their rehearsed comfort zone will be real practice for them, and this sort of thing is fun and a culture lesson as well. Meanwhile, take notes of the kinds of idioms and related vocabulary that they lack and the recurrent pronunciation and grammatical errors that they make, and end the session with a review of those things and homework for how to reinforce it.