The Interviewer's Values
Hopefully, when you were doing your employer research (see Job Interview Guide) you were able to dig up your interviewer’s salary. If you can't find out the employer's exact salary, go through the research steps in mentioned above to find the average salary for someone in her position, industry, and part of the country. Even a ballpark figure will give you the psychological advantage of sensing how she values a dollar and if she’ll feel personally threatened by your salary request.

Put yourself in her shoes: You'd probably want your subordinate to make at least 10% less than you do, right? Keep that sensitive issue in mind when you set your salary request figure.