What to say when someone ask you "How did you do that?"

Actually, a magician must not reveal how to do a trick, but when someone ask you this question, you need to say something to answer them. Here are some "good" answers:

1. Quite well,don't you think so?
2. If I told you,I am afraid I have to kill you.
3. Well......Just by luck.
4. I don't know how I did that too!
5. Camera tricks......
6. Witchcraft......
7. Can you keep the secret?
   (If they say yes)So do I.
   (If they say no)I know I can't trust you.

The 7th one is my favourite,try it!