Good quality cases and a structured review process to identify areas of weakness!

Good quality "in character" cases are the way to improve. It might sound boring but repetition is your friend here. Not 3 cases a day, but 5 or so a week with casing partners who can fully commit to staying in character throughout.

One of the classic mistakes people make in their preparation is working with people who give you clues and nudge you along a little too much. It creates a false interview environment. DO NOT DO THIS.

Anything you get stuck on in the case, work through collaboratively with your interviewer- this is exactly what would happen in a real interview. And make a note of where you get stuck over and over. For me it was the mental maths, and my ability to explain it coherently out loud as I was working.

Run focused sessions with a coach to target those specific areas you are struggling with. At the start you will usually have a long list. Get the easier ones nailed first so your overall case flow improves, then do targeted sessions on the trickier ones.

Reviewing my own cases was more useful than just doing more of them.

Try to identify one recurring weakness each week. 'get better at casing' is too broad.