I agree with Hugo, for most non conventional backgrounds (everything different from business/engineering with some years of experience, not coming right after an MBA), the main question mark for the interviewer would be the fit part. In order to work on that, my suggestions would be:
- Try to understand in depth what the consultant job/lifestyle is about. Ideally you may want to organize a conversation with a friend in consulting; if that’s not feasible, you may find a good amount of information on PrepLounge and Quora on that
- Prepare in advance on a good number of fit questions, ideally with experience candidates on PrepLounge or an Expert
- Keep a journal with mistakes and improvement and work on them each day
Besides that and the usual case preparation, coming from a not-business background I would concentrate on the following:
- Math. As you mentioned, that’s a critical part interviewers will check from non-quant backgrounds to spot potential weaknesses. The best thing would be defining a daily programme of at least 5-10 mins for math, so that you can keep in shape.
- Communication. Consultants have a specific, structured way to communicate. They use a lot of numbers and do not provide excessive long answers (As an example, the typical beginning of the case is: “In order to help our client, I would like to focus on three main areas. Number 1 we may work on [FIRST TOPIC], Number 2 on [SECOND TOPIC], Number 3 on [THIRD TOPIC]. If this is fine for you, let me go deeper in each of them.”). Communication of structures with no numbers or too long/unstructured answers will be penalized.
- Business terms. You may find business terms challenging not coming from a business background. In order to work on that, it would be ideal to read a good amount of cases from Consulting MBA Handbooks (there are several available for free online), create a list of all the main terms you are not familiar and analyse the topics.
As for the actual case preparation method, a potential programme could include the following:
- General understanding of the process: get a general idea on what a consulting interview is about
- Resources: Victor Cheng free videos, PrepLounge Resources section
- Learning structures and main fit questions
- Resources: Victor Cheng Look Over My Shoulder, MBA Handbooks, PrepLounge Resources section, Expert sessions
- Practicing with live partners to apply knowledge and improve communication
- Resources:PrepLounge P2P interviews, friends preparing for consulting
- Final review to eliminate the last mistakes
- Resources: PrepLounge P2P interviews (experienced users), friends working in consulting, Experts sessions
As for the time required, in order to be able to receive an offer from MBB, you will probably need to put 150-200 hours, starting from zero, working on your own (less if you have experienced partners/experts). Below you can find more information on that:
Hope this helps,