say "Its Magic"

^ agreed.
I haven't had anyone ever ask me that. I'd problly just say were i learned it. Book or movie or whatever. Might not say which though.

Larry Jennings has great patter for his Homing Card. When he is asked where he learned his magic, he simply states, "My dad!" Then he can begin his Homing Card. The patter goes kind of like this:

My dad taught me a trick one time that used 4 red spot cards and the Ace of Spades. I said, "Dad, the Ace of spades is the hard luck card, I'm not going to use it! I'm just going to use these 4 red spot cards!" and I placed the Ace of Spades back on top of the deck. My dad said, "Son, for this trick you have to use the Ace of Spades!" and he waved his hand over the deck and said, "Back Ace!" and just like that, the Ace was back in my hand!

If you know the effect of Homing Card you will understand what I'm talking about. If you don't know the effect, hopefully this small example of patter can give you a few ideas for doing another trick when someone asks, "Where did you learn that?"

Spec: Where did you learn it?

Magi: I spent a couple of years at Hogwarts...