So I have just added a firewall rule using ufw. How do I know whether I have to do additional steps to make this rule also automatically present after reboot? 

(2nd question, but less important to me: If they are needed, which steps?)

For example: Do I have to check for installed/enabled/configured iptables-save? Do I have to put the rule into /etc/ufw/? (where?) Is there a rule like: If I am using Ubuntu, then ufw will always remeber state after reboot?

I am not used to work with ufw or iptables-save. I just read rumors in forums and the man page for ufw.

If you have to assume an operating system for your answer then please assume Ubuntu 16.04.