Quiz show auditions are not knowledge tests, or not only. Producers are casting a programme, and the person who gets the seat is usually the one who is both good enough and watchable — which are separate qualities.
The written test is a filter, not the decision
Most shows open with a general knowledge paper under time pressure. It is designed to be too long to finish, so speed matters as much as accuracy. Practise answering fast and moving on rather than perfecting each question. Clearing it gets you into the room. It rarely gets you on television.
They are casting a person
The interview stage is looking for someone who can talk, who has a reason for being there, and who will not freeze when a camera is pointed at them. A prepared answer to ‘why do you want to do this’ is worth more than another hundred capital cities. Being likeable on screen is a real criterion, and it is not the same as being confident. Producers are wary of people who seem to be performing.
Practise the format, not just the facts
If the show uses a buzzer, practise with one. If it uses a ladder, practise deciding whether to answer. The specific skill the format tests is the one auditions expose. And practise answering out loud with someone watching. Silent practice prepares you for nothing that happens on the day.
Apply to more than one show. Selection has a large element of luck in who else turns up that day, and a rejection from one is not a judgement on your knowledge.