You can often use 'old' ideas from a topic that you have already prepared to answer a new question. Take this question for example:
We haven't prepared for this question before, but I can think of a few previous topics that might help us. Maybe you could describe a visit from a family member during a festival, or you could talk about a visit from a friend who is interested in the same hobby as you. Can you think of any other previous topics that we could use for ideas?