Dean O’Gorman and Aidan Turner will be answering questions from fans about The Hobbit: The Desolation of Smaug later today (Sunday, December 1st) from 1:15pm PST / 4:15pm EST / 9:15pm GMT. (Sounds a bit like a Reddit Ask Me Anything session, except on Facebook.)
All you have to do is keep an eye out for the thread on the official facebook page for The Hobbit then jump in with your question.