Talking about sex is always difficult with a girl who is more conservative. However, you have to read the girl. A couple days ago i got a girl to tell me nearly every place she's had sex, what's her favorite position, what she likes and doesn't like in bed and how many times she masturbates. With this girl i was direct but i did it through a method called the "Question Game".
The "Question Game"
MO: To get the girl to tell you things about herself while she learns about you at the same time.
Rules: The questions you ask must reveal something about a person. Eg. You cannot ask "what did you eat for breakfast today". Second, you cannot ask the same question back at a person. Eg. If i asked "When was your last BF?" she cannot ask "When was your last GF"
Note* This is a little tidbit for us to laugh at. Never did i say in the rules that you couldn't lie. That means you can sugar coat the truth a little if she asks you something. NEVER TELL HER THAT SHE CAN LIE! If she's on the ball she'll figure it out. But most girls will divulge their intimate secrets pretty easily.
Now, how does this game lead to the topic of sex. First begin with underlying sexual questions. These can be like "when was ur last kiss" "When was ur last bf" "How many relationships have you been in" These light questions can go on for a bit and you can judge how ur girl is reacting. The second stage is more prominant sexual quesitons or acts but still going easy with the detail. "When was the last time you made out" "Have you ever been really attracted to one of your teachers/friends/neighbours etc..." "When is the last time you had sex" etc... Then, again watching her Comfort level, move into more sexual questions with detail. "How many times do you masturbate" "are you horny alot" "have you had sex in public". You can even get into really really intimate subjects if the girl is comfotable. "Whats your weirdest fantasy" "Have you ever had sex without a condom" etc...
This is a good way for both you and her to talk about sex. And you are in control to comfortably lead the questions where you like. If you are talking about sex questions, so should she. Note* if you are, and she isn't, slow it down a bit, you're making her uncomfortable. Then you can scale back ur questions another notch. Never let the game go too far too fast, or go away from creating Sexual Tension. If you start talking about favorite movies. End the game. If she starts asking you really personal stuff fast, end the game. Tell her you can't talk about that stuff this early in the game (creates attraction) or move to Kino and Close.