Fake it until you make it, but don't lie. Being dishonest during a negotiation will cost you.
In the recently revised and updated book, "The Only Negotiating Guide You'll Ever Need: 101 Ways to Win Every Time in Any Situation," Peter B. Stark and Jane Flaherty write: "The more confidence your counterpart has in your honesty, integrity and reliability, the easier you will find it to negotiate."
When you develop trust, you can more easily accomplish what they say is the ideal outcome in almost any scenario: win-win. So don't use deception for short-term gain, because, they write: "It does not build long-term relationships or encourage your counterpart to come back and negotiate with you again at a later date."