Start by practising the following in front of a mirror:
'That's a good question...'
'I'm glad you asked that...'
then add:
'...but I'm afraid I can't speak to that.'
'... but I have no recollection of that.'
'... but I did not see that email.'
'... but that happened before I became Chief Executive.'
Try to keep a straight face. This will be difficult for anyone with a modicum of shame.