Start with the irreplaceable files
Make a short list of what would be difficult to recreate: photographs, documents, project files and any exports you deliberately keep. Write down where those files live now. Some things are inside an application rather than an obvious folder, so use that application’s export or backup documentation. Do not assume that copying a desktop folder captures the whole computer or every account setting.
Choose the destination intentionally
An external drive can hold a separate copy, while a cloud service has its own upload, account and storage arrangements. Decide which method fits your files and how you will access the result if your main device stops working. Capacity is one requirement; connector support, filesystem compatibility and how you will protect sensitive data also matter. Read the relevant operating-system and device instructions before preparing a drive.
Name the copy so future you understands it
Use a clear folder name containing the date and the source device. Keep a short note stating what you included and what you deliberately left out. If you maintain several copies, distinguish them by purpose instead of naming every drive “backup.” You should be able to answer which copy is the most recent without plugging in three disks and investigating them all.
Check rather than assume
Microsoft’s external-storage instructions recommend verifying the copied files by browsing the destination. Go a little further in your routine: locate a few important files and confirm that they open in the appropriate application. Keep the original until you have checked the copy and decided the next step. A completed progress bar is useful information, but it does not tell you whether you selected all the folders you intended.
Make the next copy easy
Put a repeatable reminder in the calendar system you already use and choose a frequency that fits how often your files change. Follow the device instructions for safe disconnection. Keep the storage device somewhere appropriate rather than permanently loose in a bag. Review the plan when you change computers, accounts or applications. The important habit is knowing what is protected and how to retrieve it, not owning a particular brand of drive.
Check the source
General planning advice. Exact model documentation decides compatibility and setup steps.