In my experience the easiest way to add sexuality to a conversation is with innuendo and double-entendre. It's hard to explain how to do it since it is very situation-specific. A conversation doesn't have to be explicitly sexual to be sexual. it's actually just a lot more fun to hint at things and then have the conversation drift in that direction as opposed to just saying "hey lets talk about sex or something sexual"
If innuendo isn't your style then just go direct with questions:
"If you could change anything about your body, what would it be?" - Most of the time it's something sexual like breast/butt size, either way it gets you talking about her body.
"What do you think of breast implants? My friend is considering getting a pair and I was saying..."
"Have you ever watched porn born before?" - Either way she answers, you grill her for being a nympho or a goody two shoes for watching or not watching porn.
~Antithesis
