Walked into my first proper interview with a printed list of twelve questions and felt prepared. Thirty minutes later, I had twelve answers that said almost nothing, because I had been so focused on the list that I stopped listening to what the person was actually telling me.
The question list trap
Relying on pre-written questions creates a false sense of control. When your subject says something unexpected and interesting, you skip past it to stay on schedule with your list.
The lesson was uncomfortable: questions are a starting point, not a script. A good answer should always generate the next question.
What happens when you over-prepare the wrong things
Spent hours reading background material before one interview and almost none of that research came up. The subject had moved on from the story I had read about. Arriving with rigid assumptions about what the interview would cover meant missing what it was actually about.
Any solid news and information portal will tell you that the best interviews often go sideways from the original angle. That sideways turn is usually the story.
One thing worth doing differently
Record the interview with permission and listen back immediately after. Hearing where you interrupted, rushed, or failed to follow up is genuinely painful and genuinely useful. Do it once and you will not make the same mistakes twice.