IPTables

Working with iptables can be bit daunting in the beginning. considering the mammoth of options and use-case scenario it opens.
Get some sneak peak at the following

http://www.netfilter.org/documentation/HOWTO/netfilter-hacking-HOWTO-3.html
This will let you know, a high level design of IPTables. This should be good to guess how packets actually trace its path in the protocol stack. In case you still have concern as the sequence involved for selecting the tables, check below.

http://www.iptables.info/en/structure-of-iptables.html

http://inai.de/images/nf-packet-flow.png

In all this should be good for any to start refering to man pages and fire their own "hello world" tables.

But debugging would still be inevitable, and so would the following entries too.

iptables -t raw -D OUTPUT -p icmp -j TRACE

iptables -t raw -D PREROUTING -p icmp -j TRACE;

Enjoy the starving nights !!