What is a plausible first step in decoding the notes?

Identifying repeating characters or symbols is a logical first step in decoding notes because it allows you to look for patterns that could indicate a substitution cipher or some other encoding method. In many decoding scenarios, repeated elements can hint at significant letters or words, providing clues about the larger structure of the text. This method is foundational because it enables you to start breaking down the code into manageable pieces. Once you understand the frequency and context of these characters, you can begin to make educated guesses about their meanings. This approach is rooted in traditional cryptography techniques, making it a sound strategy for unraveling encoded messages.

While organizing the notes in chronological order might provide context, it does not address the actual decoding process. Similarly, rewriting the notes upside down or burning them would not contribute to the understanding of the encrypted content effectively, as they divert from systematic analysis that leads to decoding.