Great little series of tutorials - had a DNS server up and running in 1/2 an hour.  Just to help others a couple of additional pointers:

1/ Test your system using the host and/or dig command (use man host/dig for details) before your connect up to rest of network.

2/ Set your DNS entries on the LAN side of  the firewall if you are using your firewall as the DHCP server.  Leave the WAN side alone.  If you are using this in a small private network (such as at home or in a small office) it is probably sufficient to have one internal DNS server so you can point your 2 DNS entries on the DHCP server with the first at your internal DNS server and the second at your internal Gateway address (usually the firewall.)

If you do this and assuming that you are using dnsmasq, then if your  internal DNS falls over, you will still get external name resolution.