I was once asked to address a group of post-docs looking for jobs outside of academia on the subject of 'how to negotiate your salary.'  Frankly, I thought that was a pretty odd request.  It's like asking "Hey Uncle Doug, give me some tips on how to hook up on the first date."  When you are coming to a new organization without a lot of business background, you are bringing a lot of skills and training, but not a lot of proven performance.  You'll be hired on your resume and skills and maybe your references, but you will be promoted and get raises based on your performance.  So I'm afraid you don't have a lot of leverage when you are negotiating your first salary.

That said, here are a couple of pointers if you are less than thrilled with your initial offer: