In one of the establishing shots of Stryker's house a second floor window can be seen broken and a figure of a body lying on the ground below. This is from the aftermath of Stryker and Brooke's murder, but, obviously, this happens much later in the film.
When Brooke paints her nails in the bathroom, she takes polish off her right index and middle fingers. A shot is shown of her polishing the middle finger. The next time you see her middle finger there's no polish on it and she starts to polish it again.
When Tara is fighting off the killer, she grabs a piece of wood and batters her assailant with it. The piece of wood is way too light, showing it may be balsa, to do any harm. It also sounds too light when Tara drops it.
At exactly 1:13:30 in the movie when the character of Tara is trying to escape from the killer inside the prop house she comes upon two doors with glass windows. At the bottom left of the screen a man from the crew can be seen sitting on the floor watching the actress play the scene.
At the very end of the film, the silhouette of a man holding a boom mic is visible on the left side of the screen when Patti is doing her comedy routine in the mental asylum.
(Seen via Academy 1.375:1 ratio) a yellow microphone can be seen above the heads of Jonathan Stryker and Samantha Sherwood when walking into the hospital reception.
When Stryker and Sherwood see Dr. Pendleton at the beginning of the movie, a microphone is clearly visible above them for several seconds after they sit down.
When Brooke is arguing with Monty the agent, there is a mic above Monty's desk in the first shot of him.