Every subject we talk about requires visualization. All events evoke a picture. You must be able to clarify and color this picture for yourself and the listener. For example, if you are narrating the experience of a day spent in Paris, you must be there (or have been there) yourself in your fantasy. Otherwise, how can you possibly take someone else (the listener) there? If you talk about climbing the Eiffel Tower, see yourself (and others) climbing it. Smell the rarified air as you ascend the tower. Hear the hundreds of footsteps of people coming down past you as you continue your climb to the top. When you get to the top, you take in the panorama of Paris at its most glorious. If your description continues with experiences on the ground, feel the presence of the French people and smell the aroma of freshly baked bread.
In contrast, if you are reading a World War II script describing a fierce, deadly battle, place yourself there in your mind. Soldiers fall, wounded and dying, all around you. Cannons. Rifle fire. Machine guns. Grenades. You must react to it. The listener will react with you. Live the experience in your mind. It’s all about empathy—the ability to experience as your own the feelings of someone else. The best actors in the business fully understand and make use of this ability in every acting challenge they encounter.