Well, for starters you'll have to spring for a nice restaurant (above).
At the right moment hold her hand, look into her eyes, and with all the earnestness you can muster, say the following without deviating from a single word....
YOU: "You know, I have a fantasy about you. Do you want to hear it?
[She says she does]
YOU: "I'm waiting for you in your living room. It's night and the room is dark except for the coals of a dying fire that smoulders in the fireplace. You emerge from the back wearing only a towel. Your inky black hair is shiny with water from the bath, fingercombed back."
[She makes a joke of it, but you continue in earnest, slowly and deliberately.]
YOU: "I want to drown myself in your taste, in your scent, in the feel of your skin. I want you to come to me, and you're unable to stop yourself."
[At this point, you need to...intensify. Never lose eye contact. If you have it in you, deliver "The Look."]
YOU: "In my dream all my focus is on you. I sense that a border has been crossed, and we both know it. I tell you to not to think about reason and logic. Don't think about what's proper or improper..."
[Now lean in.]
YOU: "...just clasp my cheeks between you palms. I tell you that I want to feel the heat of your hands race through my body from my face to my toes. I want to feel the fever of the night! I want to haul you over to me and slant my mouth over yours in a kiss."
[She's struggling to make a joke of what you're saying, but she can't. She's mesmerized.]
YOU (V.O.): "I tell you to drop your hands from my shoulders and resist if you think you can, but I know you can't, because there's a longing in you that you can't deny."
After that...after that......well, it's time to end the post.
BTW: Sorry there's no attribution for the terrific animation at the top. I can't remember where I pulled it from!