A research interview can be a huge advantage in having a more rounded paper. It can also help in finding out what you need to know about your subject from someone who has experienced in first hand. I have never done a real professional interview for a research project before. My experience is very limited. However when I have conducted an interview, I've found that keeping the interview more like a conversation between friends promotes better results. Having your questions laid out and planned before even the interview takes place is a must. Knowing the subject of the research project is key to success. Knowing the subject helps keep your questions on the main point and it will help ask follow up questions that might come up during the interview. Also being able to think fast and come up with questions on the fly and from the interviewees response helps greatly to find more in-depth answers. Taking detailed notes to the answers that the interviewee gives also helps keep you on track to continue asking the questions needed to dig deeper into the interview.  The last thing that has helped me in conducting an interview is being able to put together all the information that I gathered from the interview into something coherent. Being able to convert the notes of the interviewee's answers into a high grade paper is the second most important skill I've learned over the years. Being able to interview a person has never been my strongest skill, but with practice I've made it a skill I can continue through out my life.