Check out the maps below.
My office building, the Kaufman Management Education Center, is between two red sandstone buildings (Bobst Library to the west and Tisch Hall to the east).
As shown in the fully detailed map, 44 West 4th Street (Business school), which is at the intersection of 4th street and Greene Street, is different from 44 Washington Square South (Law School), which is at the intersection of 4th Street and MacDougal Street. You want to get to the former.
Subway: This is the fastest means of transport in Manhattan. Click here for a subway map.
Cabs: Simply tell the address to the cab driver. As mentioned above, some cab drivers are confused between 44 West 4th Street and 44 Washinton Square South.