Dawkins actually explains in more details at this site:
http://www.simonyi.ox.ac.uk/dawkins/...in_stars.shtml
“The American conjuror James Randi recounts in his book Flim Flam how as a young man he briefly got the astrology job on a Montreal newspaper, making up the horoscopes under the name Zo-ran.
His method was to cut out the forecasts from old astrology magazines, shuffle them in a hat, distribute them at random among the 12 zodiacal signs and print the results.
This was very successful of course (because all astrology works on the "Barnum principle" of saying things so vague and general that all readers think it applies to them.)
He (Randi) describes how he overheard in a cafe a pair of office workers eagerly scanning Zo-ran's column in the paper. "They squealed with delight on seeing their future so well laid out, and in response to my query said that Zo-ran had been 'right smack on' last week. I did not identify myself as Zo-ran... Reaction in the mail to the column had been quite interesting, too, and sufficient for me to decide that many people will accept and rationalise almost any pronouncement made by someone they believe to be an authority with mystic powers.
At this point, Zo-ran hung up his scissors, put away the paste pot, and went out of business.""