One thing that so often separates strong students from those who are just average, is the ability to see and recognise the context of their subject in society - whether through the world of work, or through its socio-economic impact. Where a weaker student is happy to stick to the confines of their exam curriculum the more impressive students are those who are asking questions about the importance of their subject, who are following developments through the media and who are doing wider reading, be it through journals, newspapers or texts which do not appear on the basic subject reading list.
Whichever category of student you fall under here, I strongly advise that you go to your university interview knowing one topical issue which is relevant to your degree subject. And knowing it inside out. Be prepared to answer questions on it, be prepared to give your own views. Pick something that genuinely interests you. Enthusiasm is a great thing and it will come across in the way you talk.
Also, if there happens to be any developments within your subject which are particularly prevalent at the time of your interview (because of a news story, for example, or breaking research) then certainly familiarise yourself with that particular subject and expect to be questioned on it. Don’t forget - you are not expected to be a world class expert on the finer detail but you will be expected to have formed your own views and to be able to demonstrate critical thinking.
Don’t forget that Momentum Careers Advice provides a mock interview service for just £70.