This one may go against every fiber in your body. But it works.
Mastering the art of silence is something that few of us do. Almost none do it purposefully.
There are some unwritten rules of communication. For instance, if we meet, you speak, then I speak, then you speak again. It is a turn-taking activity. Using silence can violate these rules in a useful way. If we fail this you-go-I-go mechanism, the other party will often jump to fill the void. Often they will do so by offering more information or elaborating on a point. That can be just the information we need.
Harder than it sounds
To use silence meaningfully, you have got to be comfortable not saying anything. Or at the very least, taking your time ro reply. The point is that the unwritten rules of communication will make your negotiation partner a little uncomfortable, prompting them to keep talking and revealing information they may otherwise not have offered.
You should focus on being able to deliver at least four seconds of straight-faced silence in any situation. When you first try this, it is going to feel weird. Fight the urge to speak.
You don’t need to wait until you find yourself in a negotiation situation to try this out. You can use it in any conversational situation where you want the other part to offer a little more information. You can maintain eye contact for the full four seconds - - but make sure that you don’t come across as aggressive. Smile.
Inevitably any sense of aggressiveness triggers a defensive mechanism in your negotiation partner that is psychologically akin to the armadillo-approach of turning itself into a hard-shelled ball.
You can’t negotiate with people who are on the defense (and that is true whether you want to get paid, or create any other sort of change).
Keep safe, keep talking.