Unless an individual engages an interview without notice, there is a need for research with good background and knowledge.
Learning what you can about the person, or topics will help to put you on the correct footing.
What style do they like to adopt in interviews? And what has been said on these subjects before?
We need factual information when we are trying to hold someone in authority to account and to challenge them on their assertions, to get them to explain clearly what they are talking about and to support any case they want to put to forth.
Various types of research can help to prevent stock responses from going unchallenged:
Killer facts, produced at the right moment are highly effective way of challenging a guest’s argument.
Judicious use of opinion polls may indicate that some politicians are out of step with what the public wants.
Statistics can also be used, with care, to present a counter argument, or new available data or developments.
Case studies may be useful by making it hard for a person to argue that something is absolutely not the case when you present an example showing that it is.
Accurate past quotes, replayed in context, can illustrate that someone in authority has changed their mind, been hypocritical, flip flopped, or even misled the public.