Not sure it's as profound to others as it was for me, but my biggest lesson in negotiation was the idea of negotiating in bulk. If, say, there are 20 points to work through, the idea is to know before the negotiation starts which of them you're going to insist on, which you're willing to barter for, and which you're ok to lose (i.e. barter with).
As opposed to fighting through each of the 20 items one by one...