Teens, like most people, lie for several reasons: to get away with something, to gain more freedom, to establish independence. According to PsychologyToday.com, lying intensifies during the teen years because teenagers don't want to have to deal with their parents' rules -- and it might seem a lot easier to lie than to disappoint their parents.
Establish clear rules about lying from the beginning. For example, let the teen know that if he does something inappropriate but admits it, you can deal with it. However, if he lies about it and you find out about it later, the repercussions would be much more severe. Psychology Today recommends treating lying as a serious offense and letting your teen know you won't tolerate it.
Present him with proof of the lying, if you have it. For example, if your teen went out driving without permission and got a ticket -- but never confessed to it -- show him the ticket and ask for an explanation. If he lied about owning something and then you found that article in his room, show it to him. Even if you have proof of the lying, you should still ask your teen to confess. Accepting that he lied is important -- it will make him take responsibility for his actions and behavior.
Set reasonable expectations. If your house is more like a military camp than a home, your teen will end up lying because he feels it's the only way to get any freedom. As your teen grows and becomes more responsible, give him more freedom and responsibilities. If you let him make his own decisions, he'll be more likely to trust you with his problems and might not feel the need to lie to you.
Keep your cool when your teen confesses to a lie. If the first time he admits to lying you go crazy and turn the situation into a three-hour screaming or confrontation match, chances are he will never confess to lying again. Instead, take a deep breath and let your teen know you're disappointed -- then talk about what happened and what prompted the lie. Unless it's a major offense, punish the lie, rather than the original offense. That will send the signal that lying is worse than confessing in your eyes.
Don't use tricks to get the truth. That might work the first time around, but that will also send the signal that lying is OK. For example, don't try to trick your teen by saying something along the lines of, "I already know what happened, but I want to hear the details from you," when in reality you have no idea what's going on and you are fishing for information.