People like to talk about themselves, but they need to remember that the person they're conversing with might use it against them. In my opinion, it's a very important trait to learn, both how to prevent yourself from giving out information and how to get it out of someone.

Pay attention to someone if they keep stuttering or "forgetting key" parts of the statement they're making, getting others to fill in the blanks is one of the easiest ways since our minds just want to do that. So you intentionally pretend to have difficulty remembering what you're saying and let the other person tell you.