The unspoken rules of being a tourist in New York City: ‘What is wrong with people?’

Trip to the Big Apple shaping up nicely? Flights, hotel and dinner all booked?

Great. But now for the part the guidebooks don't tell you — things tourists do that drive locals mad.

The answers are courtesy of an "r/AskNYC" Reddit thread started by a user asking: "New Yorkers — what's the one thing that instantly annoys you the moment you step outside your door?"

The thread was quickly flooded with brutally honest comments from New Yorkers keen to air their grievances.

And faux pas by tourists featured heavily.

One top-ranking mistake was simply failing to fit in with the rhythm of the city while on foot.

For example, one user remarked that what made them angry was friends "walking four in a line down the entire sidewalk like the cast of Sex and the City and not letting people get around them".

Another similarly exasperated commenter said: "I just encountered four people walking abreast, not fast, on a narrow sidewalk. There may have been an actual growl. Honestly, if they hadn't moved, I was considering barking."

Making sudden sidewalk stops to "take a picture or to look up at 'how high the buildings are'" is another no-no, as is walking slowly "while glued to your phone".

Visitors make mistakes negotiating the subway, too.

For instance, one commenter suggested tourists should figure out how MetroCards work "before they crowd around a turnstile".

And they shouldn't slow down while descending stairs to a platform when they see that their train isn't there, as people behind might be rushing to catch one that’s about to leave.

Once you're on the platform, say the thread contributors, let others off before you board, take your backpack off, and "if you are standing in front of an open seat on a crowded car, sit down, because you're not doing anyone any favors, you're just making it more crowded".

And don't stand in the doorway. Move down inside the car.

Rented a car? Remember that New Yorkers get around on foot, so be alert at crosswalks and only use the horn when absolutely necessary.

One user remarked that what angers them are "cars that damn near run you over in the crosswalk even though you have the walk signal", and "when they actually yield to you, the cars behind that person beep incessantly at them to mow everyone on the crosswalk down".

Another user concurred, adding: "Yeah, this one raises my hackles. Like, you want this car to run me over? You're so impatient that vehicular manslaughter is your preference?"

A lack of awareness at some tourist sites is another cause of frustration.

One user remarked: "Seriously, taking selfies at Ground Zero. What is wrong with people?"

Commenting on the thread, Ivan Martinović, New York City resident and business owner of Lifestyle Moving & Storage, said: "Tourists don't realize just how important flow is to city life.

"The second you walk out your door in New York, you're part of the system. There's no pulling over without consequences.

"We don't hate tourists — but we do expect them to keep up."