IELTS Speaking - interview tips
Speak until they stop you, don't just answer the question and stop. Behave as if it was a driving test –keep going straight until told to turn right, left or park.
It is quite possible that you have to speak about something you have never heard of, or have no opinion of. If you don’t know the subject – tell the examiner immediately, so he could ask you another question. If you don’t tell him and start trying to speak, he might think that it is not a knowledge problem, but a language problem.
However, certain communication skills should be used at that circumstance.