If you are configuring IPTables (or any firewall for that matter), you should always start with a block all rule. Within IPTables, it is very easy to do:
/sbin/iptables -I INPUT -j DROP -m comment --comment "Blocking all traffic by default"
This simple rule will block all communication to the server so be sure to create a whitelist for yourself as well. The last thing you want to do is block all traffic, including yourself. :)
This approach help set you into a security mindset and forces you to create a whitelist model for access. Changing your mindset goes a long way to ensuring a secure environment for your server.