here are some that I do just with the roles reversed since you are a chick talking to a dude
"so what's the crazyest thing you've ever done---
I mean like with a woman"
start a convo about kisses and kissing. get him to relate that to you, then when he does come out with "well that sounds exciting-then what"
talk about a pice of fruit you ate that day, after a few minutes start describing the shape, if it was hard or soft, what it felt like when it went in your mouth-I'm sure you get the idea.
bring up a convo of a vacation you went on once. and then talk about how when at this one part of it you noticed a bed or a place to hide or go under the boardwalk or something and then be like "I wonder what we could of done under there"
Ask him how long can he last, or when he gets hard what does he think about. Ask if he ever pictured a celeb nude and why. Ask him his most embarrassing story of private matters. Like getting caught, or playing truth or dare. Ask him if he was ever handcuffed and didn't like what the girl was doing.
You don't need to revert to sexual questions to keep a conversation interesting.
As far as sexual questions go though, every teenager learns the only thing that's really ever brought up is masturbation experiences and sexual experiences with others. There really isn't a whole lot to talk about.
last time you masterbated, what sexual positions do you want to try or enjoy, do you enjoy giving or recieving oral more, would you prefer me shaven, waxed or natural. the best questions put him on the spot and take him by surprise