After Geary is fired and is walking out of the jail, he stops and talks to Bellick. At the bottom of the screen you can see something round and white, but neither Geary nor Bellick are carrying or wearing anything white. This is the blimp of a boom mic. A blimp was used to cut down on wind noise because they were outside.
When T-bag and C-note plays poker, a card is unintentionally flipped up so you can see what it is. T-bag is then forced to deal a new card. That card is the Ace of spades. But in the next shot, where C-note picks it up, it is the two of diamonds.