I just got back so I can help you with this one. If you qualify under the visa waiver system, make sure you have submitted the advanced passenger information with your airline (this includes your address in NY, passport number). On the plane, you will be given a green card to complete and a customs form - be totally honest and consistent on these. If you make a mistake, you can get another card when you land. At immigration, the stewards will tell you where to stand - i used to be scared at this part, but it is all good. They will take your photo, and your finger tips with a scanner for their records. You then get your bags and hand in the customs form as you leave baggage reclaim.
Once you are through, there is an information desk for transport. You can join the line to get your own cab, but there are also shared cabs which are about $20 into the city and they take you to your door. Last time I went, this was very quick, the cab filled up with 11 people and I was the first drop in about 30 mins. Last week however, i had to wait 30 mins for the van and then the driver drove for an hour around the different terminals to pick up people - and then got to the city. It really depends on your budget and time table.
There is also the air train if you do not have too many bags.
I hope this helps
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