When you start an interview, find out what you're interviewing for. Typically, the person who writes and publishes a job description is not the person making the hiring decision. Ask the hiring manager what the goals are for the position, and ask who the new hire will work most closely with so you know who'll have the biggest say in whether or not you get hired.
And, if you get the job, remember that it could change all over again. Immediately. So don't ever assume you know what your job is until you investigate. The only constant about your job description is that you must be invaluable to your boss in order to succeed.
