How do I get my child to be honest with me?
First, set the proper example of being honest in all your dealings; not just with your child but with everyone around you. Just as Paul told Timothy in being a preacher he must, "be an example to the believers in word, in conduct, in love, in spirit, in faith, in purity" (I Timothy 4:12), the same hold true for parents in order for them to teach their children. Your child watches you constantly and mimics the things you do. If your child sees you lie to get out of a difficulty, guess what the child will do when he perceives himself to be in trouble?
Second, expect honesty from your child. We fault our government because it says drugs are wrong while at the same time handing out free needles. Well, parents are sometimes guilty of the same thing on a smaller scale. When a parent never accepts a child's word and tells the child, "You always lie," the child soon learns to live up to his parents expectations. Yes, children sometimes lies, so deal with each lie as it arises on an individual basis, but in between show your child that you are expecting him to tell you the truth by accepting and acting on what he states. This doesn't mean a parent should be gullible. God warns, "If a ruler pays attention to lies, all his servants become wicked" (Proverbs 29:12). So, expect truth, but don't let lies go unpunished.
Third, punish lies consistently when they are discovered. "A false witness will not go unpunished, And he who speaks lies will not escape" (Proverbs 19:5). If a child lies to get out of doing homework, make sure he gets the homework done, not only that day but for the next two weeks. When the child complains, say, "I want to believe you when you say you'll get the work done, but you didn't last ______ and you lied about it. I was very disappointed. You will have to show me that you can do your work for a while and that I can return to trusting you, then we can go back to a more normal routine." A child that repeated lies, or defiantly lies, may have to be punished to a greater extent by spanking if a good consequence to the misdeed can't be determined.