Your first salary negotiation presents a unique problem. 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.
Read on for some things that might help you get a better offer and check out my Salary and Job Offer Negotiation Workshop.