As you prepare, you will need to learn the answers to 100 questions about American history and civics. You should also study spelling words related to American history. Luckily, study guides are available for free at the U.S. Naturalization website. There, you can find study materials, classes, and advice.
There are definitely many study materials available online, but the U.S. Naturalization website has the official questions and it is free. Both aspects are perks!