It's much less difficult in situations where you aren't live - negotiating via email, for example, gives you time to think through ramifications and scenarios.

It's much less difficult in situations where you aren't live - negotiating via email, for example, gives you time to think through ramifications and scenarios. I talk quite a bit to people negotiating offers, and the overwhelming majority get into trouble when in a live setting. I agree that you are only influencing a relatively small percentage of the outcome in most cases (perhaps higher than 10% though), and at least part of that 90% you refer to consists of the image created when you were first introduced to the employer. Your resume, profile, even your previous employer's identity - that data gives an employer an initial impression of your price tag and influences where negotiations may go. This is even before the interview.