Hi there,

You need to be ready with your “three whys” per the below article:

https://www.preplounge.com/en/articles/tell-me-about-yourself-interview-question

Importantly, know why you're interested in the firm, what your goals are, and be ready to talk about yourself.

The best thing you can do is practice with someone! Nothing beats having someone “throw you off” with unexpected questions so that you can just learn how to react to whatever comes your way!

Behavioural questions like “why consulting” and “why the firm” could be asked. Boutiques typically specialise in a particular sector or a function (e.g. Delta partners specialise in telecom industry, Simon-kucher in pricing strategy) so would be good to be prepared with questions related to interest in respective sector or function 

Thanks