How do I prevent non-buddhists from going against fourth precept? As we know fourth precept is the one precept that the Bodhisatta has never said to have broken since he started cultivating Paramita. 
When I need to prevent a Buddhist person form lying, I state the above statement. And that is the reason that I was also prevented by telling lies. 

But if we need to prevent a non-Buddhist person from telling lies or  going against fourth precept, how can we do. How can we motivate him/her not to lie?
Simply ask him whether he likes to be deceived and cheated if some one else did it to him. If someone cannot be trusted would you act on what he says. How comfortable would he be to have to put up or deal with a person who is trying to deceived him. Lies cannot always be kept under wrap and if it surfaces what might happen. This would be a better way to a Buddhist also.