To close a deal, you have to read every reaction and body language of the other side. what is the most important skill needed to do so?

Understanding customer pulse and need . As mostly clients try to confuse you by various signals so whenever you decide to go for closing go for a kill and try to push customer to make a decision on same day as if you give them time they come up with various excuses or push of more discounts which will delay process of sale

so understanding the situation and reacting is key skill needed when you negotiate and dont play your cards upfront once they are done with with their all gimmicks then you show it and close the deal