Scripted answers have never been an good option for speaking. The examiner wants
to test your ability to think and speak well.
DON'T USE BIG WORDS
Yes, you must demonstrate your knowledge of a great vocabulary but do not use complicated words without knowing their meaning.
DON'T WORRY ABOUT YOUR ACCENT
Your accent is not important unless it hampers your ability to speak.
Be confident while communicating with the examiner.
DON'T SAY "I DON'T KNOW"
It is always advised to say something than saying "I don't know".