Several curse words are dubbed over with British words, though the actors are clearly saying something else (notably Lang saying "sod" dubbed in place of the "f-word"). (This only occurs in the U.S. PG-13 version of the film. Versions in Canada and the UK have no overdubbing and so the said dialog matches the mouth movements.)
Though the movie is set in Massachusetts, when the ticket agent at the ferry asks The Ghost for his choice of ticket type, she uses the British words "single" and "return" instead of the United States expressions "one-way" and "round-trip".
When the Ghost arrives in Edgartown in the borrowed BMW and pulls up in a parking lot, his vehicle is shown blocking another car parked at right angles to his. In the next medium shot, his vehicle is shown a good 6 feet or more further back and not blocking the other vehicle. In the next medium shot, when the Ghost turns his vehicle around to follow the GPS instructions, he starts from the original position blocking the other vehicle.
When the ghost writer and his agent (Rick) meet in the first scene, in a bar/restaurant, the agent has the glass almost empty of water, but in the next image (filming angle changed) his glass is 3/4 full with water.
The black car chasing The Ghost through the woods changes models. Early in the chase, the car is a Chrysler LHS, circa 2002. When it boards the ferry, it is a Chrysler 300, circa 2009. (It's possible that two sets of bad guys are following the Ghost, but that possibility is not highlighted.)
When the Ghost is driving out of Paul Emmett's home we can see the rear wiper which is stopped on the upper position, but when the same wiper is seen in the view from inside the car it's stopped on its proper position.
When the Ghost gets dressed after the night with Ruth he puts on a solid ivory-colored shirt. He then leaves the house in the host's BMW. When he is seen checking the manuscript just outside Emmet's house, he is wearing a patterned (checked) shirt.
When the Ghost takes the BMW out for the first time and stops on his way to the hotel, there is a parked car to the side of him, and he is blocking the car's exit. The film then cuts to the car interior. A moment later when it cuts back to an exterior shot, the parked car has gone.
When we first see the abandoned BMW on the ferry viewed from the the bow of the ship its front right wheel is parked straight, hard against the yellow lane divider. When we see it alone from above/behind the vehicle is more skewed and across the left-hand line.
When the Ghost stands outside Paul Emmett's house and looks in the mailbox, the letters have all been sent to Belmont, Massachusetts, with a zip code beginning with "023". But Belmont's zip code is 02478.
The investigation of a UK ex-Prime Minister by the ICC would be precluded by a cooperating British government (which implies, inter alia, the conduct of a British investigation). Article 17 of the Rome Statute states that cases are admissible only when a state's own court system is genuinely unable or unwilling to investigate or prosecute an alleged crime.
When CNN is showing how the various markets did, it list the Dow down slightly less than 50, then the S&P also down slightly less than 50. If the S&P was down 50, the Dow would likely have been down between 400 and 500.
The Ghost uses a PC when he interviews Lang, but later when he uses the Internet, the search buttons and and the mouse cursor have a "Mac-like" appearance. While the Windows version of Safari has the same buttons and the cursors on a PC can be changed, it is highly unlikely.
When Adam Lang emerges from the limousine to address the reporters, Amelia Bly crosses behind him and stands to the left. In the next shot, which shows the remainder of the press conference on television, Amelia is standing to the right of Adam. However the news camera's POV is different from that of the initial shot of the characters taking up position and Bly's positioning is not inconsistent.
Lang mentions an article in the "London Times". While it's true that Londoners call their newspaper only "The Times", he was in the US, where "The Times" is taken to mean the New York newspaper. Lang said "London Times" for the benefit of his US audience.
Ruth's accent changes randomly between very English posh and slightly Estuary (lower-class). This could be a clue that she has had to 'improve' her accent as she has ascended Lang's ladder and finds it difficult, as English people do, to keep up the pretence, especially at times of emotional stress.
When the ghost gets in the BMW, the BMW Connected Drive starts up immediately. However, it takes some time to start this up; in order to function properly, it has to connect to some satellites. The BMW Connected Drive can not work whilst in a garage (there is no contact with any satellite whatsoever to give directions).
The goof items below may give away important plot points.
When the Ghostwriter is using Google to search for information about connections between Hatherton, the CIA and Paul Emmett, he first searches for "Hartherton + CIA" and then for "CIA + Paul Emmett" (both times without quotation marks). Since there is a space between the "+" and the following term in both cases, applying the "+" operator does not have any effect on the search results, compared to using no "+" at all. The Ghost would have had to delete the space and enter "Hartherton +CIA" and "CIA +Paul Emmett" (both times without quotation marks) to get results that are more specific.
When Ms. Bly and The Ghost are entering the book "launch party" at the end of the film, Ms. Bly's hairstyle changes from one shot to the next; in the shots where she's wearing her jacket, her hair has small curls on both sides; once her jacket is off, her hair is almost completely straight.
In the final shot of the movie, the first car to pull up in front of the (off-screen) accident on a London street has a small square front number-plate. While there are such number plates in use in the UK - principally on privately-imported cars from Japan - this is very unusual. UK number-plates are rectangular. This is not necessarily an error. UK plates can be square at the front as well as rectangular and not restricted to Japanese imports. Furthermore, the plate has a Q prefix which is often assigned to kit cars and always to vehicles where the age or origin cannot be determined.