The best you can hope for is to cultivate a STRONG sense of your own moral judgment on the subject and hope that by the time they are teens, it's been heeded.
The socially gifted kids are skilled liars.
My DD14 regularly laughs in Machiavellian glee that she is Nick Naylor (the, er-- "protagonist" in Thank You for Smoking, which is probably not a good film to watch with this kind of child... nor, for that matter, is the Enron story, The Smartest Guys in the Room).
I don't tolerate lying, mind. We punish it. Fairly harshly, in fact. And we make it crystal clear that LYING is always, always, always, always a ticket to WORSE punishment than being caught without the lie, or confession of a wrongdoing.
But that doesn't do much about the compulsive 'fun' lying. Not sure what to tell you about that. Other than a lot of heart-to-heart talks about the trust of others, and some personal experience.
