Two situations call for final offers: when you can't do any better, or when it'll force the other side to close quickly. Either way, choose your words carefully. You don't want to box yourself in. A good all-purpose delivery: "This is the best I can do under the circumstances." It is final, but leaves room for change.
If you're receiving a last offer, be sensitive to brink-manship. Test a "take it or leave it" too aggressively, and an opponent may dig in their heels just to save face.
A little diplomacy is better. Consider ignoring the offer and continuing negotiating: "I'd also like to finish up quickly, but we still need to talk about . . . ." If a deadline is involved, become "unavailable." Or try my favorite tactic--open-ended questions: "Why did you decide to make your last offer just now?" "Under what circumstances would you make a better offer?" The answers may give you just the opening you need.
Many perceive a final offer as a high-risk gambit, but it really isn't. You can always make another. You have nothing to lose, except perhaps a little face.
A speaker and attorney in Los Angeles, Marc Diener is author of Deal Power.