The best way is to go to France, but in New York too you can improve your French, here is the method:

Everyday you say many times the same things without being bored, for example, how many times to you say 'hello' or 'thank you' , instead of saying these useful and common words in English, you learn them first in French and repeat them all day long.

You start with your morning activities: you wake up, you say hello, you ask how was the night etc... learn the vocabulary of this part of the day in French and repeat it everyday. When you are confident, go to the breakfast vocabulary, then the bathroom and you will learn the vocabulary you really need and will be able to speak French.

You will find this method for free here: http://www.frenchspanishonline.com!