G-OP
The advice I was given before I went for my tests was to be flexible in your answers. The interviewer is looking for decisiveness on your part, but the ability and flexibility to change your mind if you are presented with some new information. Give your answer and expect to be then given some more information by the interviewer. You then need to decide whether the new bit of info is crap or actually quite useful. Don't change your mind for the sake of it, but, equally, don't hang on for grim death when it becomes obvious your first answer was wrong. Be prepared to change your mind, but equally be prepared to justify the change. There is no right or wrong answer as long as you can justify your actions.
View it as a privelege - the ATCO in front of you is inviting you to tell him (or her) everything you know about your favourite subject. If you don't know the answer admit it. Don't try and bluff your way through because you won't. But, above all, try and enjoy it. I have to say I thoroughly enjoyed the whole afternoon - even the dreaded computer tests weren't as bad as I had been led to believe. Make sure you do not fail yourself before you have even stepped through the door.
Incidentally, your name sake keeps passing through the radar sector next to me and was parked outside our tower last week.