If you've never interviewed anybody, then you won't have a precise feel for what it's like on the other side.
However, this does not stop you from trying to anticipate some of the questions that might be asked.
How well are interviewers trained? In most cases not very well. How well do they prepare? Best to assume that they are prepared. Don’t underestimate them. One of the best ways for you to prepare is to imagine yourself as the interviewer. Put yourself in their position. Read the job advertisement. Read the job description. What are they looking for?
For instance, if you're being interviewed for an accounting role, expect questions to revolve around detail and accuracy, your knowledge of the subject, and your teamwork skills. If you're moving up the ladder in sales, your interviewer will want to know about your successes and results, how you overcame barriers to sealing the deal, and will be observing your body language and how you communicate.
So imagine yourself sitting in the chair opposite and asking all the questions. You'll be amazed what you can come up with and it might even give you a different perspective on the role, opening your eyes to things you hadn't even thought about.