1. Pay no attention to signs or traffic lights. Simply drive with the traffic.
2. Yes, that taxi is going to cut you off.
3. Pedestrians pay no attention to walk/don't walk signs. They cross whenever and where ever they like. The also leap from the curb into the road without warning to flag a taxi.
4. If you leave any space at all between you and the car in front of you, someone will try to squeeze into it.
5. Every horizontal surface in the city will be considered by someone a legitimate parking spot. There are almost no alleys or driveways, so trucks, delivery vans, moving vans, taxis, limos, rickshaws, etc. simply stop on the road in front of buildings.
6. Paying for parking in Manhattan will cost you the same as a hotel room in any other city.
7. People use their horns. A lot. Taxis use their horns instead of their brakes.
8. Most of the major north/south avenues are one-way and 5 lanes wide. The centre lane is designated for emergency vehicles - if a fire truck, police car or ambulance is coming, everyone is expected to clear out of the centre lane. Surprisingly, this works quite well. People get out of the way and the emergency vehicles come roaring through at high speed. Then, taxis immediately tuck in behind the emergency vehicles and roar at high speed too.
9. Use your car to get to or from Manhattan, but within Manhattan, don't drive. Walking, the subway, or a taxi will be faster and cheaper. There's probably nowhere to park where you're going anyway, and even if there is, you'll pay way more to park than a taxi or subway would cost.
10. GPS signals are unreliable in the urban canyons of Manhattan. Know where you're going without relying on GPS. With the numbered streets & avenues, it's really easy to navigate.