“But my child will just ignore me and do whatever he wants on his own.”

Never forget that you control the privileges, and therefore you control the “Yes-When deals.”  If you allow your child to wander off and enjoy freedom after he has boldly defied you, then the obvious conclusion is that he has learned that you are weak and your words are meaningless.  If, however, you set a “Yes-When deal” that you believe is not that important in the first place, then allowing your child to choose not to participate in the deal is fine.  For example, let’s say you offer, “Yes Junior you can have a dollar, when you rake the leaves,” but your child chooses instead to do homework.  He was not “hostile” or “defiant” in his choice, and his “noncompliance” was a reasonable choice that he has made.  Therefore, you may choose to simply allow him to make that choice without discord and without withholding other privileges and without “forcing” him to rake leaves.