Lost Rule #1: Never, ever, give any information to anyone, for any reason.
There are some exceptions to this. If you're talking with an enemy, you can feel free to give them all the information you know.
If you're talking to someone you like, though, the process is a little bit tougher. The only allowable way of transmitting information is to offhandedly allude to it. When someone asks what you mean, you have to act like it isn't important. Later, when they ask again, you can explain what you meant.