I’ve always winced at the moment in All The President’s Men when the actor portraying Kenneth Dahlberg says “I…uhm, I gave the check to Stans” and Robert Redford pauses and goes, “Beg your pardon?” As if to say, “Whoa…did you just spill the big beans?” One should never express excitement when a source has revealed something big. That’s like jerking too hard on the fishing pole after getting a nibble. If anything, you should indicate that the just-revealed info is almost yawn-worthy, or certainly no big deal. Otherwise you could scare them off.