HowTo save rules of the iptables?

If you need to secure your Ubuntu Server adding some rules on iptables and you want to re-apply rules after a server reboot you can install iptables-persistent

# sudo apt-get install iptables-persistent

After installed, you can save/reload iptables rules anytime:

# sudo /etc/init.d/iptables-persistent save 
# sudo /etc/init.d/iptables-persistent reload