How can I get a press pass for a movie screening?

How can I get a press pass for an advanced movie screening? I've been going to screenings for a couple months now, but I always have to get there at least an hour early if I want to get a good seat -- and I've noticed that there are a bunch of seats reserved for members of the press. How can I get a press pass? I've been writing movie reviews online for quite some time, including on Facebook and on Examiner.com, but I can't figure out how to get a press pass. Thanks!! (I'm in Boston, by the way)