I started off thinking about Harry Potter, and when it became obvious that he was about to guess it correctly I just started giving random answers to various questions and telling him he was wrong.
Then, I played again but just kept saying "I don't know". He guessed "The One Nothing Is Known About", "I don\'t know" and "Stop saying I don't know and play the game", before finally coming to the conclusion that I was thinking about "engineer Igor Chauskin".