Describe the symptoms
Note the error message, operating system and when the problem started. Say what you have already tried. Remove private information from screenshots.
Check the connection and backups
Check your internet connection and save open work. Back up important files if it is safe to do so. Mention any suspected physical disk failure.
Agree the connection first
Install remote software only from its official source and for a support session you have arranged. Verify who you are communicating with. Do not approve unexpected support requests.
Keep access limited
Close private documents. Approve the agreed session yourself and stay present. Do not send passwords or session codes through the contact form. Enter necessary passwords yourself using the agreed procedure.
End the session
Close the remote connection after the work. Check that unattended access has not been left enabled. Review the changes and next steps.