The summary.
MEMORY AND STORAGE ARE DIFFERENT PURCHASES
A computer slow with several programs open needs memory. One out of space needs storage.
Replacing a mechanical drive with a solid-state one transforms an older machine more than any other upgrade.
WORK FROM A STANDARD ACCOUNT, NOT AN ADMINISTRATIVE ONE
Anything that runs has the rights of the account running it.
ENABLE DISPLAY OF FILE EXTENSIONS
So you can see what a file actually is. A document asking to enable content is asking to run code.
GET SOFTWARE FROM THE DEVELOPER OR AN OFFICIAL STORE
Never aggregators, search advertisements, or pirated copies.
RUN A SUPPORTED OPERATING SYSTEM VERSION
One no longer receiving updates is a permanent vulnerability.
SYNCHRONISATION IS NOT A BACKUP
A deletion, corruption or encryption synchronises everywhere. Keep a separate copy the live system cannot alter, and test restoring from it once.
MOST COMPLAINTS OF SLOW INTERNET ARE WIRELESS PROBLEMS
Test the same thing on a cable to find out.
KEEP A REASONABLE MARGIN OF FREE DISK SPACE
A nearly full disk makes everything slow and eventually prevents work.