Nice! This should be very helpful for new witnesses. Just wanted to add another potentially useful tidbit.

"Redirect your stderr (and stdout) on start-up so your witness doesn’t go down when you disconnect from SSH. See the example start command below for how this is done."

You can also accomplish this by running the witness command from within a screen session. The added benefit of using screen is that you can have multiple windows for monitoring the server.

To Install
sudo apt-get install screen

Start the screen session
screen

Open additional screen window
ctrl-c a (hit ctrl-a, release and press c immediately after)

Cycle through to the next window
ctrl-a n (hit ctrl-a, release and press n immediately after)

To Detach(Use before exiting server)
ctrl-a d

As long as you started the steem binary within screen and detach before disconnecting, it should continue running after you disconnect

To reconnect to a screen session after reconnecting to the server you can use the following commands:
screen -r
or
screen -dr