(at around 35 mins) When Quentin is searching the internet, he types the search term "sleep deprivation" then presses enter, then uses the mouse to click the search button (blast off). Generally, after pressing enter, you wouldn't need to click the button afterwards to get the results.
(at around 25 mins) When Jesse tries to comfort Kris before they get in bed, he puts both hands on the sides of her face. In shots from Jesse's point of view only his right hand is on her face, while from Kris's point of view both hands are there.
(at around 18 mins) When Nancy and Quentin are talking in the school, between shots Quentin's jumper moves so that 'Joy Division' is fully visible on his T-shirt, however when the camera moves back to the position it was before, the jumper has moved back, so that you can only see 'Y Divis'.
(at around 30 mins) When Jesse runs out of Kris' room he grabs his pants and shoes. In the next scene when he runs out of the house he is wearing them without having taken the time to stop and put them on.
(at around 1h 9 mins) Sign in front of gas station states they accept "LINK", the Illinois government assistance program, where the movie was filmed. "WIC" is the Ohio government assistance program, where the movie takes place.
(at around 34 mins) When Quentin answers Nancy's phone call you can clearly see the main screen instead of the blue in-call sequence. Later he presses the phone closer against his face and the application screen appears.
(at around 55 mins) During swimming practice, Quentin is shown hanging off the dive platform at the end of his lane, listening to the coach talk. 3 or 4 drops of water rise out of the pool and fly up to his elbow, revealing that this particular scene is being played in reverse. (Also you can just make out from the top right of the screen that the coach is actually walking backwards, as shown by the string coming from his right pocket which you can see in the next camera angle)
The goof items below may give away important plot points.
(at around 29 mins) When Kris first gets slashed, the spatter on Jesse's shirt is minimal speckling on the left sleeve. However, when he goes to check on Kris, the blood has some how become huge splotches covering his shirt.
(at around 1h 6 mins) When Freddy is walking towards Nancy in the boiler area, his hand is originally closed with his index finger running along the pipe. In the next shot, his fingers are now opened, slightly trailing behind his index finger. They once more return to their closed position, following the shot.
(at around 1h) Marcus Yeon died during his last video blog, yet seems to have posted his own death. Posting technology exists with an automatic posting option. In the script, Marcus says "clicking the auto-upload button."
When Kris is sitting in her chair at Dean's funeral she is wearing diamond studs in her second piercing and no earrings in her first. When she gets up to look at the pictures the studs are now in her first hole. But she is in a dream sequence from the time she gets up, as she fell asleep in her chair, so this may be a deliberate inconsistency.
When Jesse gets Freddy's glove and arm jammed through his body, he falls down on the floor of his prison cell and you can see there's no wound on his back. Even his shirt is still intact. His cell mate does not wipe off the blood that hit him, making this the second of three times in the film where Krueger injured someone and their injuries are inconsistently presented in real life. The third incidence occurs when Nancy is attacked in the drug store. Her mother is focused on the cigarette burn on her arm, as Mrs. Holbrook and hospital personnel believe Nancy is self-mutilating, and not the slash marks caused by Krueger.
(at around 38 mins) When Freddy and Jesse are in the boiler room you can see the CG work on the left side of Freddy's face. There are green spots where the CG work should be. After that, during different spots in the film, you can see green dots on Freddy's face for the CG work.