You can catch a coach from the airport that terminates at Central Station. It takes about a hour (I think). Although I haven't taken it myself, a friend of mine uses the subway, which he reckons is safe. Both are reasonable priced.
Or what happened to me when I departed NY and went to central station to catch the coach, a yellow cab driver squeezed 4 of us into his cab, switched the meter off and charged us a good price that worked out cheaper than the coach. Probably not advisable in this day and age.