While you get prepared to answer such questions try to understand the employer's reasons for asking it. Most employers tend to use such questions on past salary as a gauge to determine your market value and read your mind as what you wish. They want to sense what salary you would be expecting from them and whether they would be able to pay you that much or not. At times it is better to disclose the salary to save wastage of time. If the employer finds it more than what he could pay for the position it is better to end the discussion and move ahead.