I would add another bonus step. Install openssh-server, and deny-hosts. Teamviewer definitely works better for most folks behind a home router, but for the folks still on dial-up, or directly hooked to their high-speed modem, or on a shared network with you, this is going to be faster for you when you need to log in to fix a config issue.
I feel that deny-hosts ought to be a pre-requisite package to openssh-server, but that's just me.
...and this one isn't going to help with keeping them from bailing, but should always be done... Configure UFW and give them a little guide on how to use it. (This should also be done in the Windows world with the built-in Windows firewall.)
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