There is a fine art to interviewing politicians. You need to understand their motivation, realise they will have a script, not allow them to complicate matters, refuse to be sidetracked, retain an open mind, know your subject, and avoid a slanging match. You are there only to uncover information in order to inform the public debate.
A journalist must learn the house rules of the media organisations they are working for. All will have a set of guidelines and a style guide. But here are general tips about starting off in journalism.