The reference interview is where you try to find out exactly what the researcher needs, since they aren't always good at explaining it to you. It takes some practice to get good at interviewing patrons. Here are some strategies to get you started.
*The important thing to remember about a reference interview is that the person asking the question may actually need more information or guidance than they are asking for. Try to solicit as much information about what they are looking for as possible. Sometimes, they just want the book they asked you for, but other times they actually need much more.