During the scene in the high-stakes private club when the dealer is caught skimming cards from the deck, the Chinese man speaks to George first in Mandarin. In the elevator the Chinese man reveals he can speak English and that George had told him to "speak nonsense with conviction." George did not address the tuna salesman first.
Barnes says that Casinos will do anything to distract a player including sending over free booze. While this is true in the United States, the movie is set in Canada, and Canadian casinos are not permitted to "give" free alcohol. Soft drinks and coffee only.
When George eats a hamburger in his hotel room you can hear the camera operator's footsteps as he walks backwards holding the camera.
In the "bridesmaid's dress" scene, the camera crew is reflected in a window.