David Stone I think addressed this, and one key point is as Lady Mystery said, hold it with the thumb and (well I use middle finger), push down a little with the index on the middle to bend it up ward and as you put it down make the NAIL of your index finger the last part to touch. This helps leave them the way they are. He also gives them a slight flick after bending them upward so it slides a bit, but remains together.
I think Gregory Wilson's "Double Take" has a bit about tabling a double. He is very casual about it, but i agree with kingjeux. Using the nail not only sort of "leaves them the way they are," but it also keeps the fleshy part of your fingre from sticking to the card.
