What to do about lying

I am wondering what other parents do when their child blatantly lies, consistently? What do you say? What is the punishment? How do you get through that secrets or lying about anything (especially serious things) is wrong??? ...before it gets out of hand. We are a blended family and the situation with the mother and maternal grandparents is awful. Supervised visitation and limited contact but they are all very manipulative and we're sure this is where she's picked it up (more than just the childhood level phase). She already sees a child psychologist for court purposes. No real input in awhile on this subject from psych, as we haven't been there to touch base. So, just wondering what other parents do even if it's not exactly like our complicated situation... Thanks in advance.