Interviewing for a clerkship requires you to be as flexible and accommodating as possible. First, if you are not at home when a judge calls you to schedule an interview, call the judge back that day or, at the very latest, the next day. The time you take to return the call indicates your interest (or lack thereof) in the clerkship and could seriously affect your candidacy.
If you are asked when you can come in for an interview, the wise response would be, "Tomorrow morning, unless the judge would be free this afternoon!" (From: Trenton H. Norris, "The Judicial Clerkship Selection Process: An Applicant's Perspective on Bad Apples, Sour Grapes, and Fruitful Reform," 81 Cal. L. Rev. 765, 779 (1993).) Seriously, you should be ready to interview at the convenience of the judge, with potentially as little as 24 hours' notice. If a suggested date is not possible for you, you should inform the judge of your conflict and request the earliest possible alternative date. If the judge gives you a range of dates, try to schedule your interview on the earliest of those dates. Many judges hire clerks on a rolling basis. Therefore, you may be at a competitive disadvantage if you interview later in the judge's schedule. Believe it or not, each year several students report that after they have scheduled an interview with a judge, but before they have had the interview, the judge has called to say that clerkship slots have been filled by candidates who interviewed earlier.
Because in many circumstances applicants are expected to accept a clerkship offer as soon as one is made, some applicants try to arrange interviews – to the extent possible – so that they interview first with those judges for whom they think they would most prefer to clerk. This strategy is becoming more and more risky and difficult to manage, however, given that there are no uniform guidelines governing the timing of interviews and offers and interviews may be compacted into a very short timeframe.