It’s crucial to back up all your important data before beginning the upgrade process. This includes all your personal files, applications, photos, videos, documents, and any other data you’d like to retain. It would be best to clone the entire hard drive if possible, using software such as Carbon Copy Cloner. This ensures that your data is safe, and that you can restore it to the newly upgraded system with ease. You can use Time Machine, a cloud backup service, or a dedicated disk cloning software for this process.