Hiya!
Huge congrats on the AC! You're clearly very cut out for this, especially considering you've already made it past the most difficult and competitive stages of the process! Honestly don't be afraid to own that fact. You've gotten this far because you're an amazing candidate and the AC is just about demonstrating that in person.
Jacob has great articles
here and
here on case studies and dealing with common questions in interviews.
The first thing I did before an AC was make a list of the different parts of the AC and all the things I felt I needed to do for each part to be prepared. I think this can help with making prep feel more manageable because you can systematically work through things.
One of the best things you can do before an AC is to go through your application again to spot anything that might be used as basis to ask follow up questions. This is particularly true for partner interviews and those interviews tend to be much more focused on getting to know you, understanding any interests you've noted in your application and your motivations for wanting to be at the firm.
Look into booking a mock interview with your careers service or even doing one with a friend so you can pick up on any areas of improvement beforehand. Also, instead of merely preparing your answers on paper, definitely talk through them out loud. I think this will help you be more confident with what you're saying on the day (because it won't be the first time you're saying it).
I also agree with what's been said about being friendly. Don't be afraid to chat to the other candidates or grad rec while waiting for assessments to start. It can be really difficult to get your personality across in a virtual AC and I do think that small things like this really make all the difference.
Good luck with your AC, we're all rooting for you! xx