Jay O’Keeffe has a written a great post called "10 Things I Wish I’d Known Before My First Oral Argument." An excerpt:
3. Anticipate hard questions.
As soon as I start working on an appeal, I create a document called "Tough Questions." This document includes every hard question I can think of, regardless of whether I can answer it. I update it constantly through the briefing and oral argument process. The goal is to anticipate every hard question the Court can throw at you, and prepare–and practice–your best answer.
I have had the good fortune to argue a significant number of cases before state and federal appellate courts, and Jay does a great job of sharing ideas that anyone who is facing his or her first – or tenth – oral argument would want to know.
Oral argument takes much more work than many people recognize. I once spent over 40 hours preparing for a 15 minute argument in the 11th Circuit – and in hindsight in needed every one of them.