Take the E train @ 53rd Street and 7th Avenue to Jamaica station (in Queens). When you arrive at Jamaice, go upstairs (use the elevator),and follow the signs to AirTrain (you will walk right past all the Long Island Rail Road platforms), and it will take you to the JetBlue terminal (#6 I believe). It is easy as can be, although the walk from the AirTrain to Jetblue is a healthy one (all indoors, there is a moving walkway). The cost is $2.25 for the subway, and $5.00 for the AirTrain, total $7.25.
AirTrain service