I like how the article gives examples of the sort of entropy players draw on to make their random choices:
> Koon will often randomly select which of the solver’s tactics to employ in a given hand. He’ll glance down at the second hand on his watch, or at a poker chip to note the orientation of the casino logo as if it were a clock face, in order to generate a percentage between 1 and 100.
The watch face is the classic one, the chip orientation is new to me. I like it, it's less obvious that you're randomizing something, and given how much poker players like to fidget with their chips the orientation is probably reasonably random.
Another classic is to use the suit of your cards, but that has problems with being correlated with the state of the board. It works fine preflop.
> Koon will often randomly select which of the solver’s tactics to employ in a given hand. He’ll glance down at the second hand on his watch, or at a poker chip to note the orientation of the casino logo as if it were a clock face, in order to generate a percentage between 1 and 100.