Simple iptables firewall ?

[TenPin]

I use these rules for iptables. I was wondering if anyone can improve on this without getting hideously complex. This machine has 2 interfaces, 1 for the cable modem and the other for LAN.

-t nat -A POSTROUTING -o eth0 -j MASQUERADE
-A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT
-A INPUT -i eth0 -p tcp --dport 113 -j REJECT --reject-with tcp-reset
-A INPUT -i eth0 -j DROP

Thanks