Here are my five (general) tips for successful answers:
VOCAL ENERGY: Don’t speak ‘over the phrase and down’ ; keep the energy of your voice sustained throughout your answer.
SUBSTANCE: Don’t overspeak or underspeak: an abrupt end is as damaging as waffle.
DICTION: Hit the last consonants in the word: these will keep your clarity and diction strong and add confidence to your answer.
CONTENT: Aim at specificity. Don’t say you’re a team player without giving an instance of your having been so. Just the one example will suffice.
PERSONALITY: Do not stare - blink. I don’t mean pretend you’ve a fly in your eye but an occasional blink will save you from seeming too concentrated, and you’ll appear more comfortable.