Do your research and know your bottom line. Research the industry standard for the positions you are applying for in your geographic area. Whenever possible, try to defer the salary question on the first interview so that you don't under or over sell yourself. If pressured, be prepared to give the employer a salary range.

I'm sure that your company offers a fair, competitive salary for someone with my education / training, skills and experience. I am also willing to negotiate for the right position.