The neg hit is the male act of deflating an attractive woman's best features in a way that is neither insulting or demeaning, but only suggests innocently or playfully that he is not phased and should not be expected to react to her features as other men normally would.
The advantage of the neg hit is two-fold when used proper and effectively. It first allows a man to distinguish himself from other men who, in her common experience, fall too readily for her because of her features. The second advantage establishes the assumption to a woman that the man using the neg has associated with, hence is worthy of, attention from other women who possess the same asset(s) that are being negged.
Every man in the room immediately noticed Jamie when she first walked in because she had a great set of tits. But while most men were fetching her drinks and being as nice as they could possibly be to win over her attention, Mikey instead decided to neghit her by asking if they were real or implants. He not only immediately got her attention, but already had a solid conversation going long before the other guys could make any real, distinguishable impression on her.