These are critical pieces of information. Consider the ramifications for your future personal wealth. You need to know the value of what you are losing by leaving your old job, the dollar value of raises that might be imminent, stock options that are not yet vested, or retirement plans that you cannot take with you. Depending on where you're moving, a lower offer might put more money in your pocket or a higher offer might have a lower bottom line. Be sure you factor those in.
Good negotiators know the art of compromise.
They are calm and confident, not scared, hurried, arrogant or inflexible. But they had a real quiet confidence about themselves. They were clear in their own minds about their skills and abilities and the value they would add to a new employer. And both of these people were successful. Now, let's assume that during the interview, you absolutely must give some sort of salary target.