In this webinar hosted by SDN with experts from BeMo Academic Consulting, you will learn a simple five-step process to help you translate your interview invitation into an acceptance.
I actually recommend taking supershuttle. it's about 19 bucks one way or 38 round trip (you do the math), but it picks you up at JFK and drops you off anywhere you want in manhattan. Taking the subway can take awhile...but then again, watch out for rush hour traffic.
Airtrain + Subway - $7 ($5 for Airtrain, $2 for subway) - Take the Airtrain to the Howard Beach Stop (Station A). Then, take the Manhattan-bound A Train subway. At Broadway Junction, transfer to the Manhattan-bound L Train. The L Train will travel through Brooklyn, and the first stop in Manhattan is at 14th St. and 1st Ave.
This option, or the ones above, will get you to your destination.
Cheapest, as stated above, is Air Train to subway but this will take a long time and is a pain. The fastest is to take a cab but its more expensive. I'm pretty sure its a flat rate of $30 + tip (it might have gone up a little but it is a flat rate mandated by the city TLC and does not include any tolls ).