Some good advice from Free Money Finance: A Better Way to Get the Salary You Want:
"I think this advice is not realistic. If an interviewer asks you point blank what your salary requirements are, you may be able to dodge him once or twice with a smooth, non-committal answer. But if he presses you (which I would do), you're either going to have to tell him or look uncooperative/obstinate -- which obviously doesn't put your best foot forward during the interview process.
So here's an alternative that I like from Yahoo -- price yourself like a house"
Read more about this...BEFORE you interview!