Hey,
Heres some guidance:
Practice alone vs with Case Partners/Coaches
After some initial solo effort (say 5-10 cases), you will get maximum value by working with a good case partner or experienced coach. Start off with cases on topics or industries you have a natural liking for (to build confidence & momentum) and then work you way into unknown topics/industries & progressively add to the difficulty and complexity. There is no magic number of cases to practice. The more the better (ideally >25) but you can cut corners here and there depending on your situation & time commitments. To speed things up, consider a good case partner or coach.
How to choose a good partner
Check out this post for plenty of tips: https://www.preplounge.com/en/consulting-forum/case-vs-case-partner-10731
Make a plan
A solid plan is important. Depending on your situation and time commitments, make a plan, believe in it and stick to it. Factor in ample breaks in between practice days and treat yourself every now and then. Celebrate the little successes. Keep peer pressure at a distance and just focus on giving your best. There are so many posts on the Q&A forum on this so please search broadly & soak in the advice. For e.g. have a look at this: https://www.preplounge.com/en/consulting-forum/mckinsey-interview-preperation-4315
Handling nerves
Its important to learn to deal with the pressure & anxiety before & during the interview process to allow yourself to give your best. Have a look this thread of some guidance on this: https://www.preplounge.com/en/consulting-forum/dealing-with-nervousness-10452
All the best!
(edited)