When you write an interview to be spoken, first, make sure you know what topic of what you should interview with your interviewee. Second, make your questions interestingly related to the topic you are to interview. Lastly, make your grammar correct. However, list down all of the questions as much as possible.
Now, when you speak to the interviewee, first, always get a ready smile, and fix yourself up before interviewing. Second, don't go too far to the topic when you are interviewing. Always read your questionnaire if necessary to avoid mistakes in interviewing.