When your child is doing something that's not to your liking, just saying "no" is likely to lead to a conflict.
Respectful parents offer their children alternatives: "Don't do THAT... Here, do THIS."
But if you lead with a "no," the "yes" may not be heard — the child will be too busy defending against what appears to be an assault on his or her freedom.
So look for ways to say "yes" FIRST — if not literally, then energetically — and don't focus a lot of energy on the "no." Let your child be attracted to an acceptable alternative rather than forced.
Now you're working with your child's nature!