Know your adversary’s case
No general engages the enemy without a battle plan based in large part on what the enemy is expected to do. Your case must take into account the points the other side is likely to make. You must have a clear notion of which ones can be swallowed (accepted but shown to be irrelevant) and which must be vigorously countered on the merits. If your brief and argument come first, you must decide which of your adversary’s points are so significant that they must be addressed in your opening presentation and which ones can be left to your reply brief or oral rebuttal. Of course, a principal brief or argument that is all rebuttal is anathema.
At the trial stage, you must initially discern your adversary’s positions from the pleadings, the conferences, and discovery, and by using common sense. At the appellate stage, you can rely on what was argued and sought to be proved below. Bear in mind, however, that lawyers tend to develop new arguments, and revise their theories, as the case proceeds upward. Constantly ask yourself what you would argue if you were on the other side.
Don’t delude yourself. Try to discern the real argument that an intelligent opponent would make, and don’t replace it with a straw man that you can easily dispatch.