The scene right after the title, when Dex and Rachel wake-up in bed together, Dex stumbling around, looks at his cell and drops it on the floor to put on his boxers and pants. You can see his cellphone, between the edge of the bed and the duvet on the floor, when he turns down the volume on the answering machine. He then walks towards the door and puts on his shirt, and leaves with Darcy's purse and his jacket in hand -- never goes back for his phone. When Rachel's phone rings again, they show a wide shot, and the phone is no longer on the floor, but the duvet is still as it was before.
When Rachel and Dex meet on the front stairs of Rachel's house (4th of July), they go for a walk. When the camera is filming Rachel from the front, she keeps her arms behind her back. When the camera is filming from her back, the arms are held in front.
Near the end, Darcy goes to Rachel's apartment. She has nothing with her. When we see her storm outside the building, she grabs Marcus' pizza wrapper and walks away. Then the shot switches to her from the back and she has a brown purse, no wrapper. The purse was sitting beside Marcus on the stoop but we don't see her pick it up.
In the last shot with Darcy and Rachel, Darcy's hair in front is down by her face. Darcy walks by Rachel and when she turns around, her hair is partially tucked behind her ear. No indication is made that she does this.
During the badminton game Dex throws the shuttle in the air to serve, contravening badminton rules 9.1.5 & 9.1.6 which state the shuttle must be hit below the waist line and the racket must be pointing in a downward direction.