After going down on your man, you let him cum into your mouth. However, rather than spitting or swallowing, keep it in your mouth, then slowly go up to his lips for a kiss, pushing his man juice into his mouth with your tongue.
Guy 1: This chick totally gave me a swiss snowball...
Guy 2: Oh dear god what is that?
Guy 1: Let me put it this way - I'll never cum in her mouth again, now I know how it tastes.