How do I prevent non-buddhists from going against fourth precept?
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.