The subway is a convenient and fast method of getting around New York City. Although subways run 24 hours a day, not all lines run at all times. Check the MTA website. It is also not advisable to ride the subway alone late at night.
Wait for subways in well-lit areas and ride the subway with groups of people or in the same car as the conductor, usually the middle of the train. Be aware of your surroundings and the people around you. For nighttime travel wait in the “Off Hours Waiting Area”, which is marked with yellow signage. These areas are under surveillance by MTA staff.
A Metrocard is required to ride the subway. Metrocards can be purchased at the Transportation and Parking Office on campus (Campus Center North) or at token booths or vending machines in most subway stations.
Subway Map - http://www.mta.info/maps/submap.html