Accessing Asterisk from outside the network

I have my Asterisk configured and contemplating opening a port so that I can remotely access * with a Travel ATA. Is there a set of best practices resources? For example, I would definitely want to stand this up on a nonstandard port (for example opening port 52525 and mapping it to the asterisk server, encrypting credentials and ???

Any pointers or URLs are appreciated.

look for iptables + fail2ban