It would depend on the situation Assuming she is ready for me to cum.
I love to talk dirty, so I might say that I'm gonna explode in your tight/wet/hot pussy.... or perhaps I might want to shoot a load on her face, tits what ever and would say I'm gonna explode/shoot/nut all over your face, tits.... You get the idea.
Once I have shot my load, I usually say that I'm gonna clean up the messs-which I do by licking and then snowballing before she swallows the cum...
If however I'm getting sucked, I just moan a lot untill I can't fucking take it and then I groan as my cock shoots into her mouth usually saying soemething like Fuck me that was good, now it is your turn.