I believe good looking in that case has several components:
- Your "look and feel"
- Your energy level and being friendly, smiling and cheerful
- Your ability to listen to the interviewer
- Your ability to ask questions
- Your interests besides career and consulting
1) Look and feel. It's the way you are dressed, the way you behave, body movement, etc. Do you look mature enough? Do you behave professionally?
Your look should be:
- Professional (Suit, fresh haircut, clean shoes, etc)
- Mature (e.g. no piercing)
- Should impress (No cheap and poor looking Zara suits)
- Should help you to project confidence - make sure that you feel comfortable in a suit. If not - practice solving cases in a suit.
It may sound obvious, but many candidates miss that. Make a video of your mock interview and show to your friends or even random people. Ask them if they would personally hire you.
2) Your energy level and being friendly, smiling and cheerful. In many cultures, it is not natural to always smile and you really have to develop that skill. Also, sometimes, when the situation is stressful and tiring, it is really easy to stop get deep into a thought process and get tired. When you get tired your pose and gestures are different and others can easily see that. The only recommendation here is to always control it.
3) Your ability to listen with genuine interest - don't ever interrupt. Listen to people demonstrating your genuine interest
4) Your ability to ask questions. The main objective is to have a good conversation and highlight your intellectual capacity and curiosity.
5) Your interests besides career and consulting. Good consultants can maintain a conversation with a client during the dinner or in a long taxi ride. They have broad knowledge, know examples from different industries and can speak on various topics. It's always good to have some personal stories that can demonstrate your passions and personal side.