Here is something I do if I screw up a double: Suppose I do a convincing double. Now I need to replace it (turn it back face down). Because I do the Daley Strike Double, which means that I do not use a get ready, sometimes I will grab the wrong number of cards. Once in a great while I will turn back over three instead of two
. Now I have an indifferent card facing up--in a face down deck--oops. What I will do (this has happened twice) is I will say to the card, "what are you doing here?" Then I will grab it and fling it accross the room and go on with the trick. Surprisingly, most people laugh and go back to watching the trick, none the wiser.