Each question will probably be related to one particular PQA. From the experience I have of these interviews, the assessor will normally ask you an opening question, for example - 'Can you give me an example of a time you have been under intense pressure and had a lot of demands placed on you?'. You will give your answer and then the assessor will normally ask probing questions to see how your behaviour alligns with elements of the PQA, marking them against the BARS.
So he may want to look at your 'emotional control', and will do so by asking relevant questions, such as 'Ok Darren, you were obviously under a lot of pressure during this event, how did that make you feel? Did you feel able to cope with the events unfolding around you?' etc. This is your opportunity to show that 'remained rational and in control of your emotions despite being under intense pressure'.
I usually prepare by chosing a different example for each PQA that I am going to be tested on, ensuring that it covers as many of the constructs in the BARS as possible. If there is a particular element that my example doesn't cover then I will have another example in reserve that I can call on if required.
You will have probably noticed during your previous interview that one assessor will be asking the questions and one will be writing away furiously. The scribe will actually be trying to write down everything that you say and he will use this to mark you after the interview has finished. So try to talk at a pace where he can get down most of the information that you are giving, but don't get drawn into looking for him to stop writing before continuing with you answer. We all tend to speed up our speech when we are nervous, but do try to keep it under control to ensure that you don't needlesly lose marks.