Speak to your child in a calm firm voice, and if he looks away, gently turn his head towards you to maintain eye contact. If he struggles, don't fight, let him go. Next time he speaks to you, ignore him. Maintain silence for about ten minutes, then calmly explain that you don't like him igonoring you, and you are going to do the same - if he stops doing it, so will you. He will eventually get the message, but you must be firm, and carry it through every single time he does this, because he will test you, and has to know that you mean it, or the whole problem will get worse. It is uncomfortable at first, but stay calm, don't shout, don't argue, just repeat your reasons slowly and calmy until he realises that you mean it. He will stop.