Continuity mistake: Carrie is in the hotel bed from her night with the French Architect, who is just leaving for the Airport. There is a shot of the small table by the bed, with the phone sitting on it. You cannot see any envelope at all resting against the phone, or visible at all. But with the next close-up, suddenly there is a large business-size envelope with her name on it resting prominently against the front of the phone. This envelope was not there previously.
Continuity mistake: After Amelita buys Carrie the shoes and Carrie turns to walk out, Amelita is standing right behind her still talking yet when the shot changes to Carrie walking out the door, although we can still hear Amelita chattering, she's no longer standing there or anywhere in sight.