Most of us work hard and pray deeply about our choice of readings, when the choice is up to us. But until you have actually read a selection aloud you don't know how it will sound. Remember, oral communication is very different from written communication. Your listeners don't have the words written, paragraphed, and punctuated in front of them. You do. They have only the sound of your voice. When you read aloud, you are translating the written thoughts into spoken thoughts. To "translate" well—to get the full meaning across and have the reading sound conversational, interesting, and natural, rather than dull and stilted—you need to practice aloud.
At the beginning, practice by yourself, because it's much easier to explore aloud when no one else is listening. When you think that you have the material under control and that your voice and speech express the ideas you're reading, it's time to have a listener, if you feel you want one. If you are a Reader in a branch church, practicing aloud with the other Reader is essential. At least one rehearsal should be in the church. But it is best for you to work aloud by yourself first —then for both to work together as a team to make the Lesson-Sermon sound cohesive.
Practicing aloud can be of value in many ways.