Trains run regularly to New Haven from New York City (via Metro-North Railroad or Amtrak) and from Boston (via Amtrak).
Commuter airlines provide connections to Tweed-New Haven Airport from many U.S. cities. Van services are available from NYC airports. You may also fly into Bradley, located in Hartford, CT, and rent a car for the approximately 90 minute drive.
Yale Law School is a short taxi ride from either the train station or the airport.
To reach Yale Law School by car, take Exit 3 off I-91 (from North or South). The exit ramp becomes Trumbull Street. Follow Trumbull Street to the end (at the fifth light - Prospect Street).
Turn left on Prospect Street. Take the first right (at the stoplight) onto Grove Street.
The Law School is in the second block on your left. Metered parking is available on Grove Street and on other streets in the vicinity; the main entrance to the Law School (127 Wall Street) is a short walk away at the corner of Wall and High Streets.
(Thanks to the Yale Law School Travel page.)