Salary discussions during an interview center around what you have made in prior positions and/or what you are seeking to earn in your next position. (The rules are different if you're responding in writing to a written request for a salary history or requirements from an advertised position.)
A salary discussion is not a salary negotiation. It can however lay the foundation for a salary negotiation. )
Employers ask salary questions to see if a close match exists between the salary likely to be offered and your expectations. Naturally, the closer you are to the employer's salary range, the more likely you will accept an offer and remain with the company.
Be prepared to disclose your salary history when asked. If your salary history differs significantly (higher or lower) than your current expectations, you must be prepared to address these differences at the same time. Keep in mind that you need to consider the total compensation package including benefits.
Often a significant difference in salary occurs when making a change in career, industry, type or level of position, geographical area, or when starting a new career. Without knowing the appropriate salary range for the type of position you are seeking, you may not be able to address variances in your salary history. In this case, you need to conduct prior research as to salary ranges for someone with your experience and skills for the type of position in the industry and geographical area in which you are interviewing. (Visit Salary Surveys and Cost of Living).
You may also be asked directly regarding your salary expectations. For example, the employer may ask: "What are you wanting to earn in your next position?" This is different than asking for historical facts like your salary history, so you have latitude in answering. In general you can use a range rather than a specific figure when discussing numbers at this stage.
Keep in mind that this is not the time to negotiate salary — you are simply answering the employer's interview question. When handled appropriately, a salary discussion can lay the foundation for negotiating the best salary later.