When K and L were in high school, we used to walk at the track almost every evening. Most of the time we wouldn't get down there until it was dark. And that's when I figured out an important part of parenting tweens and teens.
Kids are most likely to talk to their parents when they can't see the parent's reaction to what they are saying. If they can't see shock, horror, or judgement on your face; they will tell all. (Often, more than you want to hear.) If you can bite your tongue and just listen, it is amazing what they will tell you. Of course, you might be tempted to lock them in their rooms until they are 30, so use this technique with caution.
Looking back, I realize that I had learned this trick years before. I had seen it work when they were younger. Turning off the light in their rooms at bedtime had the same effect. I'd sit on the edge of the bed and just listen in the dark. They confessed or shared problems, worries, and pranks.
Another place kids talk is in the car. They can only see the side of your face. Fix your eyes on the road, and the kid will spill.
Of course, in all three of these scenarios, the challenge is not talking or gasping. Eye rolling is about all you can do, though I'm sure my eyebrows shot up a time or two.
And now you know everything that I know about raising children. Sorry, it isn't much. The girls had a good Dad and the rest was luck!