If you are a beginner you shouldn't use iptables directly, as it probably will give you more problems than it solves. Unless you are familiar with a handful of RFC:s, you should use a frontend instead.

I would really recommend you to use ufw if you don't route traffic between different LAN. It's quite easy to use and there are some useful instructions to look up. But if you do need routing, I have found shorewall useful as ufw doesn't support any routing or NAT (yet, it's comming).
The good thing with ufw is that it also supports IPv6 besides IPv4, it uses both iptables and ip6tables.

In short, use a frontend and not iptables unless you really know what you do and you know the differences between different ICMP messages.