My thanks to Bill Duncan for his kind words.
In the write-up of The Card, the Forehead, and the Salt Shaker I discuss two performance restrictions. One has to do with the shape of the table. The other has to do with the nature of the spectators. Here is that text (the paragraph with the brackets is part of the recent annotations):
The other performance restriction is this: you must size up your audience very carefully. The two people who assist you (especially the lady on the right) are going to pay some dues. A routine of this nature can be very frustrating for an audience, since they are never able to catch you. You want people who will laugh at the futility of their situation, not become angry over it. This is not a routine to use for spectators who are challenging or belligerent in nature. However, if your audience is laughing and getting into the spirit of the performance this routine is perfect.
[I cannot overemphasize the importance of the above paragraph. One night at Illusions, Chris Moore (one of the founders) was in attendance. He had not seen the salt shaker routine, and I was anxious for him to see it. There was only one more table to perform for, and as I sized up the couple I was sure that the woman was going to hate the shaker routine. I did it anyway, so Chris could see it. It was a miserable experience. When I do this routine at magic conventions, I always try to watch part of the set of the performer ahead of me. I scan the audience, looking for a woman who will be a suitable helper. I try to never choose blindly.]
Another important point, which I have not discussed in print, is the importance of what you say. I never
say the words "I put the card (wherever)." I only say, "The card is (wherever)." To some degree this softens the "stick it in their face" aspect of a routine of this type.
For those interested, The Card, the Forehead, and the Salt Shaker is available in The Complete Workers Series ebook on my website. The routine has been extensively annotated.