Make a computer inventory of not only what you aquire, but what gets away and what you still want. Don't buy art as an investment. Start informing yourself of that part of the contemporary NewYork artworld that seems most appealing. Get the Gallery Guides free from the galleries. Visit the galleries and museums.
Business cards are necessecary.
If you can identify the works that interest you, then you can meet the artist to arrange a studio visit. Never pay the asking price. Then make an offer you believe is fair. Don't forget, you are in a buyer's market. You are the buyer.