How can giving my child time to finish a task help him listen better?

Interrupting an involved child can lead to resistance. So if you see your child is really engrossed in something legitimate (her homework, texting his friend about homework, his Lego construction), have some flexibility. Wait until you see your child is a little less engaged in the task. Then say your request. Just ensure that your child doesn’t take advantage of the situation. (If he appears legitimately engrossed in an activity, give a time limit: “I need your attention in a minute, please.”