Some great replies by other members here. I take kind of a comedic approach to those kinds of questions from spectators. On one hand, I don't want to tell a bald-faced lie, since most everything I do depends on sleight of hand, subtlety, math, or in some cases, clever gimmicks, but on the other hand, I don't want to flat out say, "No, magic isn't real." So, on those occasions that I am asked the question, "Is magic real," or something similar, I jokingly say, "Why yes, of course. In fact, I can magically triple your money. Just place all your money here in my hand." As they brighten up and/or act as if they are reaching for their money, I say, "I will take it home tonight and if it works, I'll send it to you in the mail." Never fails to bring a smile...