[susan53]

Stay with things which are within their (and your) experience and can be easily expressed using the structures and vocabulary that they know. For example :

(For present simple) : Describe a typical day in your life. / How do you usually spend your holidays? / What do you like doing in your spare time?
(For simple past) : What did you do at the weekend / for your last holiday? / for your holidays when you were a child?
(Mixed past forms) : What's your earliest memory? / Can you remember your first day at school? / What's the most exciting / surprising thing that's ever happened to you? / Tell us about a time you had to do a journey in really bad weather.
(Mixed forms) : Have you ever seen a UFO (when/where)? Do you believe they exist?
Why (not)?

The discussions will always be more productive if the students have a mdel to work with. So - before you ask them to discuss, tell them about something that happened to you on the same thing. Check they've understood what you've said, and then ask them to talk about the same thing.

For example : for the topic Tell us about a time you had to do a journey in really bad weather I tell a story about a three-day horseback journey I once did where, because of sudden bad weather, we got lost in the mountains. I check comprehension by giving them photos of the journey and asking them to put them in order while they listen. after my story, I then ask them to think of a journey they've done in bad weather - and start giving prompts to stimulate ideas : Maybe it was a time when you were driving and it was very foggy or it started to snow ... maybe you were travelling by plane and the plane was delayed by the weather ... or maybe you were on a plane and there was a storm. Once I see (by the looks on their faces) that they've all remembered a story, then I put them into groups and get them to tell each other their stories. Each group can then choose the best story to tell to the class. them