Walk around Midtown at lunch. Try to capture the conflict of human and vehicular traffic. Try to experience it, if you can, as a driver or front-seat passenger. Experience the rush hour on foot, on the subway, on the laconic buses, and in the back seat of a taxi. Go to a less-packed region (Broadway between Houston (House-ton, PLEASE!) and 14th, maybe--your friend will know) between 2:00 and 3:30. Get a feeling for the way New Yorkers jaywalk and adapt to the current state of the traffic lights, the different way they move at the lights and the crosswalks. How would someone who is hungry and maybe over-caffeinated fare in that cauldron?
Learn the New York way of ordering coffee: 'Regular' means with milk. Light, white, light and sweet, etc. Find where the city allows food carts and trucks to operate, and see which are popular at lunch. See the human and vehicular jams, if you can, when there is an event at MSG. Get disoriented by the lights at Times Square, and by the traffic crossing the sidewalk at parking garages. See the stupid tourist stuff (including women wearing nothing but body paint) that the city and the courts have conspired to allow near Times Square. (Is your protag desperate enough to consider this? She'll need an artist to do the work and share her take with.)
See Washington and Union Squares if your character might possibly go there.
Take the subways at the rush. Include trips in the financial district where the stairs to the street are one passenger wide. Especially take all the subways, at various hours, where your protag may go. Have her realize she chose the wrong (wastefully expensive) options on the MetroCard. Have her take the wrong train, or a train that's been re-routed; have her end up in Brooklyn or Queens (look for stations with the same street names--WkiP will help here). Include an elevated or street level run. Have her fall asleep and end up in Coney Island--or a bad neightborhood. Have her goggle at the subway map, and a map that shows the entire rail transit system.
Have her ask directions on the street and experience both kindness and rudeness.