New York natives fold our pizza to eat it.
Pizza by the slice is a bit of a religion in New York and us natives fold our slice in half lengthwise to eat it. This technique makes it easier to eat and walk at the same time, not to mention it allows the grease to drip out before biting into it. Transplants and visitors are not required to do this (holding a slice flat is just fine), but there is zero excuse for using a knife and fork to eat pizza.