As for asking questions to elicit responses, you should try for conversations where many tenses are required. Ask for a hypothetical story, for example. This would require terms like "if I were" "then I could" and the like.
You could start with: "What will you do tomorrow?"
Potential answer: "I will go walking."
Question: "And, if the weather is bad, would you still go walking?"
Now, you want an answer such as: "If the weather is poor, I could still go walking. In this case, I would have to take along an umbrella. However, if the weather turned nice, I could close the umbrella. Then I would have gone walking on a rainy day which changed to being nice."
I don't know what level you have to check for, but using conditional and passive usually indicate a good grasp of any language.
Just a few thoughts! Good luck!!
- For Teachers