IPtables Script Review Requested

[carmstrong]

Hey guys, I'm entirely new to iptables, but I've managed to write a little script. I'd like reviews on anything I've missed or done incorrectly before I run it so I don't lock myself out of the machine. Here goes:

#!/bin/sh
IPTABLES=/usr/sbin/iptables
echo 0 > /proc/sys/net/ipv4/ip_forward
#flush current rules
$IPTABLES -F
$IPTABLES -P INPUT DROP
$IPTABLES -P FORWARD DROP
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 80
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 21
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 110
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 25 
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 22
$IPTABLES -A INPUT -j ACCEPT -p tcp --dport 53
$IPTABLES -A INPUT -j ACCEPT -p udp --dport 53

Anything I've forgotten? This is a machine that won't need to be routing anything. Also, should I just install iptables with apt-get install iptables? And then how would I go about getting my iptables script to initialize on system startup?

[sarumont]

Looks good from here. Nice simple firewall.