In the very first scene as Dean sits on the deck, the tackle box at his feet is open with the lid resting on its propped handle. However, during the conversation with Castiel, the lid is flat on the deck, then goes back to its previous position once Castiel is gone.
When Sam and Dean are going after Jimmy in the Impala they appear to be alone, but moments later Anna appears in the backseat. If you look closely in between the actors, before Anna appears, you can see the shoulder of the actress in the backseat meaning she was in the car the entire time and did not appear out of thin air as angels usually do.
After Castiel returns to Jimmy's vessel, and Sam and Dean are driving down the road, the Impala has no taillights.