You kind of have to play it by what you know about him, but a good one is to talk in a breathy voice and tell him how much he turns you on. Do it with a slight sense of urgency, almost like you couldn’t help yourself from saying it. Throw in some sort of expletive for good measure. Something like “oh god, I love when you touch me like that” or “fuck, I want to feel you inside me so badly.” It also pays to get specific. Mention specific body parts or acts that you’re into. Use the word “cock.”