I'm a first year geographer at Cambridge and so I sat my interview last year, so I'm more than happy to help a bit. I'd definitely like to preface that the interviews can feel daunting in advance and it's important to see it as less of a judgement day situation and more like a conversation with academics who are very senior in their field and passionate about geography. By looking at it this way, I found the interview so much less stressful and that helped me to settle and make fewer silly mistakes because of the pressure.
I'd really recommend looking at random graphs, maps, photos etc from areas of geography that you mentioned in your personal statement or areas of geography which your interviewers are specialists in - there generally will be a major link between their subject specialisms and your interview questions. When you look at the figure, I'd try and work out what it's suggesting just based off a first look (e.g. if it's a graph then maybe literally just what the variables are, or if it's a photo then a basic look as to where the location is, etc), and then look at what the relationship is between the graph and extra information about the photo and how it could relate more widely to an area of geography. Breaking down your thought process like this is a great way to practice how to think in the interview, since your interviewer will care more about how you think over what you think.
Mock interviews are also a great way to practice the interview situation, but be careful to arrange an interview with a teacher or friend or family member - it's better to do a mock interview with someone that you don't already know, since in general it's always a lot easier to talk with somebody you already know rather than an unfamiliar interviewer, as you'll get in the real thing. I did mock interviews with a geography teacher from a different school in my area through an exchange programme which my sixth form was in with others in the region, and this was a better representation of the formalities and communication which you will likely use in the Cambridge interview.
Best of luck guys, and if you have any more questions I'd be more than happy to advise!