For obvious reasons everyone will have a different answer; it will depend on your teaching style, grade interviewing for, and past experiences. The interviewer will be looking to see if you have a plan, you know how to implement it, and if you think that discipline is an important part of the position. What I have found from coaching clients is they fail to provide a clear action plan that can be backed up with examples. Also it is important to find out what is the philosophy of the school or district, this will give you some additional information. A few things to bring up when answering this question is the following:

It is important to develop ground rules the first week of class, this allows the students to understand what is and isn't acceptable behavior.

These rules are discussed and agreed upon with the students, this makes the students accountability and responsible. You may want to touch on your philosophy of classroom discipline. This of course would depend on your style; you will have to be honest with yourself. But you may believe that you reduce negative behavior by offering the students a intellectually stimulating, organized, and respectful environment.