Before you can negotiate salary, you need some reference points. What's the average salary for that position? What is the salary range? What is your salary potential if you pursue that career path?
What makes this especially difficult is that the same title (e.g., "Medical Director") may have a salary range of $120-150k in one industry and a range of $250-280k in a different industry. So, if you check online salary calculators (like the ones found on Salary.com, Monster.com, etc.) you won't find an accurate salary figure for a position like "Medical Director" because that position can mean 100 different things in 100 different industries.
Did you know that many non-physicians hold the title "Medical Director"? Some are nurses, others are pharmacists, some have a PhD, and others don't have any clinical background. These individuals are director-level executives for the department of medical affairs.
So how do you get some salary data for a particular industry? You need to speak with recruiters and other human resource professionals who can get you grounded so that you have a realistic expectation for salary. I (and other career coaches) work with physicians all the time to discuss salary because I work closely with recruiters to help physicians get the best salary for every position.