Tony Schutta, parenting coach wrote a good article on dealing with defiant children.  I found the article on the internet and wanted to share it with you.  It's simple , easy to understand and numbered, making it easier to read.  Here are the first three ideas.  You can go to the link to find out the other 6 ideas.

1. Use positive communication. Try phrasing your parenting command in a positive way versus a negative way. For example, if your child says “Can I watch TV now?” instead of just saying, “No. You can’t.” you could say “You can watch TV after dinner.” Or “I can tape this show for you to watch after dinner.”

2. Give the child two choices. As a parent you can pick two choices that are equally acceptable to you and offer them to your child. The child is less likely to be oppositional if they feel they have some control over the situation. For example, you could say, “Would you like to do your chore before school or after school today?”

3. Reflect the feeling back to the child. Sometimes showing compassion for the child by reflecting back what they’re feeling can be helpful. You could say, “You’re irritated right now because you can’t finish building the Lego tower. It’s hard to leave a project before you’re done, isn’t it?”