No offence Nic but I couldn't help but laugh when I read the title of this thread
This is just off the top of my head so it's nothing special but you could force a card with a Svengali deck, deal the cards into two piles, get the spectator to choose (the appropriate) pile then deal these into a row. Place down the ferret in front of the row and the first card he sniffs or touches with his paw is turned over and it is seen to be the selected card.
Just an idea
