How about talking about shared-hobbies SERIOUSLY?
To avoid "taught lessons", you teachers have to make learners speak. To do so, I suppose it is effective to give desire to insist something to learners.
Of course the hobbies may not match well. It's possible to occur. But, "love" could be a solution then. Most of people have some ideas or opinions about love.
For me, some political problems are very exciting to talk, however, that would be too much.
Or, how about asking about culture of where the learner lives?
In this case, you are able to estimate the way how the learners answer(or probably make mistakes). It means you can prepare for the lesson easily.
And you can show the correct way by telling the culture of your country.
I know you work as a professional and so I'm afraid that my ideas are too basic for you. But, they are what I had in English classes in my high school and I felt effective to improve abilities.(This is the result! I'm writing English! Yay!)