When you prepare your maps, create a sheet of paper or similar which contains the course description for each map section. Break down your primary and alternate routes, control points, terrain features, distances, and elevations. If you have a double-sided clear map case, then place that in your map case behind your current map, facing out, and upside down from your map. This way you can flip the map over, and your course description and route notes are immediately available.

If there are any specific rules or navigational items to be aware of (eg off-course routes that you are forbidden by race rules to take), you can place that info there, so it's available for review during the race.