On getting in
It's not a big secret that the leading consulting firms are notoriously difficult to get into. On average an office the size of a few hundred consultants receives a multiple of their size in first round applications per year. Ultimately, only a very low percentage of these applicants end up getting a full time offer. To maximize your chances of receiving an offer it helps to understand recruiting from the firm's perspective. The interview process starts long before you hand in your application.
When the recruiting team receives your application and decides on whether they should grant you a first round interview or not, they will gather all available information they have on you. This could include your performance during recruiting events (even if they tell you otherwise at the beginning of these events), or the view that somebody in your network who works at the firm has on your skills and fit with the company. The key thing to understand here is that this is less important if you already tick all the boxes, but could really help you if you're one of those 'we're not quite sure cases'. Therefore, the latter is where networking would really pay off.
Let's assume you check all the boxes and receive a first round invite. You have a killer resume and performed well during recruiting events. Somebody at the firm might even have lobbied for you. Maybe you already secured an offer from one of the firm's competitors, but would rather not work there due to personal preferences. None of this will matter much when that first interview comes around. You start from 0. Mess up the case? You're out. The interviewer doesn't see a fit with the firm? You're out. The interviewers are trained to make a fair and thorough assessment of your performance. They might like your personality, but will not push for you if they feel that your analytics were weak. Something that is helpful to know is that interviewers like people who have done interesting things out of passion (and not to build their resumes).
Working, and even interviewing people who pursue their passions makes consulting life more fun. Lucky for you, you don't have to climb Mt. Everest to be interesting. Even something like playing chess and organizing a local tournament suffices. Highlighting how interesting you are is also one of the most important functions of your resume (it will also ensure that it is actually read and used during an interview). Unfortunately, a good GPA also falls in the 'being interesting' category, since nobody wants to work with somebody who can add 1+1.
Some of the major dimensions on which you will be measured during the interview are analytics, communication, presence and impact, likability, fit with the company, and maturity. Basically, it all boils down to the following: would I staff this kid on my next case? Luckily, you'll already have developed most of these dimensions during your time at university. Otherwise, why apply in the first place? Although it could be wise to practice some of the typical behavioral interview questions, don't overdo it. A big part of whether you'll tick this box is simply the personality that you've developed over the years. As for the analytics, it helps to practice a reasonable amount of cases with a good partner.
Key here is finding a good partner, as the quality of your practice interview will depend for 80% on how well your partner can simulate an actual case interview. What is an reasonable amount of cases? My personal view is keep the amount of cases in the teens. Your 25th practice case will not determine if you're going to make it or not. At some point other interview skills become more important. Instead of doing 50 practice interviews, make sure your basic arithmetic is flawless. Too many qualified candidates have not made it because they stumbled on something like a 34% margin on a 3 445 000 turnover.
Disclaimer: I'm a consultant at a European MBB office, therefore some of the points mentioned above might not necessarily apply to the US
Potential future topics in case of sufficient interest
On performing well
On the firm, projects, and impact
On exit and development opportunities