It's also knowing how to ask. There's the stereotype in interrogations in TV and movies that you bully or trick people into telling you their secrets. Real interrogations involve forming friendships and sympathising with people. People will tell you anything if they think you will understand and empathise with them. There's also some other tricks like being silent etc etc. You guys should read that stuff, super useful even outside of dating.You'd be surprised what people will share with you within 5 minutes of knowing them when you ask enough questions.