Don't run any other services that you don't really need. Use command lsof -i to see what ports your computer is listening on. Make sure you understand what you see. Turn off what you don't need. I put this just ahead of item 6 in the Top 6 tips, which would be installing a firewall.
Firewalls protect services from unauthorized access.
It's better to just not run the service if you don't have to, and it's a lot easier for the average bear.