I am continually astounded to hear evening newscasters use these terms incorrectly, and I cringe each and every time it happens. These terms are also unfortunately misused in newspapers and magazines, as well, bringing my flow of reading to a screeching halt with the wrongness of it.
Use “who” when referring to a person: Mary is the girl who is dating Jim.
Use “that” when referring to anything that is not a person – a dog, a chair, etc.: Can you help me find the ball that rolled under the house?
Thank you, and please pass this on.