I prepared for this and all my other interviews by making a list of all my extracurricular activities and what I learnt from each one, so that I had plenty of examples to draw from when I was asked behavioural type questions (eg. When was a time you...)
Keep it natural and conversational, definitely DON'T recite pre-prepared crap about how you're passionate about accounting.
Prepare some questions to ask (things you're genuinely interested in, not just for the sake of it)
And yeahhh those are my top tips for acing all your cadetship interviews lol. Also it gets a lot easier with experience, so even if you don't do as well as you hope, just take it as a valuable contribution to your career, and you will definitely be better the next time round.