It often helps to do a pre-interview with a guest, although some experienced interviewers prefer not to, as they feel it may kill spontaneity.
However, you don't want your interview to become an undirected "chat." As you finish your research and plan your questions, ask yourself, "What is my goal in this interview?" The answer should be more than "To fill x minutes." You need a direction, information you want to reveal, or a side of the guest that is significant that you want to show. Some guests feel nervous about an interview and want to have some control over the situation. You may get requests for the actual questions in advance. However, this is not a good idea as it will take away from the spontaneity of the interview and produce a feeling, as you can get rehearsed responses. The guests should have a general idea of the areas you will discuss so they can be prepared, and if you've done a pre-interview they probably can guess several questions you will ask. In some instances, showing the questions ahead of time may be the only way you will get an interview with an important guest, but you will have to decide if it is worth it.
For the beginning interviewer, the pre-interview is a valuable tool. It can be done in person, over the phone, or via e-mail. The pre-interview allows you to introduce yourself and build rapport with your guest, and it can help you avoid asking inane questions that will show your ignorance. This is a good time to check name pronunciation and any other difficult words (jargon) that might come up during the interview. If you've done your research, you might just say, "I'd like to talk about___________." You can inquire about the guest's points of view or experiences with the subject. Often in discussing experiences you will stumble across things that would be interesting to include. But don't get wrapped up in a lot of details such as where the guest grew up, went to school, or his or her favorite hobbies, unless these are pertinent to your goal with the interview. Keep considering how each idea relates to that goal. It's appropriate to ask if your guest has some experience or story that would be interesting to your audience. You may not use it, but these stories can serve as padding and may also help your guest open up to you. Be careful not to conduct an interview instead of a pre-interview. Once you get a basic sense of something you'll be discussing, move on to the next area. Save some of your curiosity for the show.
Remember that in the interview there will be occasions when ou are asking questions to which you already know the answers. You are the audience's representative. Audience members will not know as much about the guest as you do. So ask questions or clarify statements that will help them understand and enjoy the interview.
Be sure to tell the guest up front how long the pre-interview and the interview process will take. This is especially important for television—since you are working with many people and pieces of equipment, the chances of things needing to be redone or taking longer to set up are greater than in radio. Communicate a realistic time frame to your guest. People—especially busy people—need a reasonable estimate of the time involved so they can plan their day.