Nearly every professional interaction you have during your career will involve a negotiation of some sort. Whether you're closing a million-dollar deal with a client, bargaining over your own terms of employment, or delegating duties among your coworkers, the key to successful negotiation is possessing intelligence. But intelligence doesn't mean just having smarts. It means knowing your opponents inside and out: how they respond under stress, what tricks they try to pull to catch you off guard, and how to negotiate a fair deal that makes both sides happy. It means knowing what they will ask for before they ask, what they are willing to give before they give, and where they will draw the line before they walk away from the table.