You should say:

• What is it
• Which song or poem it is from
• How you know it
• And explain how you feel about it

Sample Answers: https://ieltsquangtri.com/describe-a-line-that-you-remember-from-a-poem-or-a-song/

You should say:

• What the promise was
• To whom you made it
• Whether it was easy or difficult to keep
• And explain why you made it.

Sample Answers: https://ieltsquangtri.com/describe-a-time-you-made-a-promise-to-someone/