Your confidence to speak is the most important trait in interview (& conference as well). But remember, whatever you speak should be defensible by you. Never self contradict. Be straightforward in your answers.

Be thorough with your life; make a list of your, successes, good times with friends/family, decisions you have made and reason behind them, your favorite subjects (and why so), strengths (why).

Hobbies are vital. Know info about your hobby well.

Never criticize anyone. IO will try to make you criticize somebody but you do not do that and keep sticking to your logic for defending.

Keep a grasp on the current affairs (global plus local) and form your own logical analysis about it.