I originally posted this in response to a question, but at the suggestion by Sunnydolan I made it into an essay.
I don't think anyone here can say that they haven't been faced with the question, "How did you do that?" I've had a thought about the best way to tackle answering it and I present my thoughts to you:
There are two types of people who say, "How do you do that?" One is the person who says it out of astonishment and can't think of anything else to say. The other is the person who seriously want to know how to do it. If it's out of astonishment, take what they said as a compliment and just smile at them without saying a word, and then move on. Treat is just as if they'd said, "Man, that was a great trick." That's pretty much what they meant. Now, obviously that won't work if they actually want to know. Younger children fall into this category. They won't be satisfied with a smile as an answer. They really want to discover the secret.
If they genuinely want to know, I'll either say, "Magic," "I'm not gonna say," or "I'm not really sure," depending on how I feel at the time, or what kind of people I'm with. There are a bunch more of these kind of things to say littered about the Outs and One Liners Forum
. One line that crops up frequently in that forum, which I disagree with, is, "Very well, thank you." I used to use that but as I matured I realised that it was a rather arrogant thing to say, and just plain annoying.
If they don't like your answer and persist with the questions, I move onto phase B, which involves giving bogus explanations that are clearly fake, like "Magnets," "It's a stooge," (quite funny if there's no one else involved other than the one spectator) "Mirrors" etc. I personally act as if I've rapidly though of the explanation on the spot.
At that point, some will give up.
The remainder of people left are those who either want to know for the sake of knowing, or those who actually do want to know because they are magicians, liked your effect and want to use it themselves. If they genuinely want to know, I may point them in the direction of the magic dealer I bought it from. I still won't reveal the secret. If it's the kind of person who wants to know for the sake of knowing (i.e. children), I'll either act like a broken record and say, "I'm not gonna tell you," as this is a tried and tested was for getting rid of people, or I will question why they want to know.
If they want to know for the sake of knowing, I'll tell them to go away and live with it, probably in nicer words. If they want to know because they want to show their friends at school/work/the bar then I'll tell them that if they want to do tricks for entertainment they have to start at the bottom like everyone else. I might point them in the direction of a beginner's book of self-working that most people know anyway. That's enough to put anyone off, as people who aren't serious about learning the trick wouldn't want to spend years practising just for one trick.
That's my definitive way for dealing with people who want to know "How I did it".