I just had to follow the instructions to set up the gateway. This is what I used for the WORKIT AP (eth0 is my wired WAN connection and ath0 is the wireless LAN):
# Delete and flush. Default table is "filter". Others like "nat" must be explicitly stated.
# Flush all the rules in filter and nat tables
iptables --table nat --flush
# Delete all chains that are not in default filter and nat table
iptables --table nat --delete-chain
# Set up IP FORWARDing and Masquerading
iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
iptables --append FORWARD --in-interface ath0 -j ACCEPT
# Enables packet forwarding by kernel
echo 1 > /proc/sys/net/ipv4/ip_forward
Also, while instructions exist for both iptables and ipchains, you will find yourself using the iptables rules since ipchains was RIP after Linux 2.4 came out.