As much as they would possibly give you, right? In my newest article for Philly.com, I discuss some strategies for answering the salary question. How you best answer depends on what you already know and how far into the interview process you are when they pop the question. You'll almost always have more leverage later in the process (once the employer is more invested in you as the idea candidate and you have a better sense of what the job would really look like).
I'm a certified career coach based in Philadelphia. I started my own practice to help people land their dream jobs and achieve their individual definitions of success.
I also keep this blog with my musings on changes in the employment landscape, advice for job seekers, links to other career-related articles, and anything else that catches my interest.