What precum should be called. When giving a blowjob, and not wishing to swallow the jizz, take the slight increase in pre- ejaculate to be a salty warning. Not only does it stop you from coming across like a terrified amatuer, it also means the guy is less likely to hold your head and foil your escape.
"Did you spit after sucking off Craig? Cos jizz tastes like the sea, it's awful"
"Didn't need to. I just paid attention to the salty warning and let him spunk on my face"