How do I maintain and protect my server/droplet for the long term?

Imagine a customer so ignorant that he could install a droplet but then didn’t know what to do after that on a regular basis? OK, stop imagining. That’s me. Droplet is installed. DNS seems to be set up adequately. Dev environment works, and mysite.com/index.html is visible to the outside world.

Now what do I do on a regular basis to keep bad guys out and my system healthy? Here’s the checklist I’ve come up with but I’m sure it’s hilariously naive and inadequate.

• Install logwatch
• Install OSSEC and configure it.
• Set up a firewall.

Then, every day or every couple of days do these things? But what’s missing from this todo list?

• View OSSEC logs daily
• View logwatch logs daily?
• Every couple of days, check for updates:

$ sudo apt-get update
$ sudo apt-get upgrade