Documentation and tools.
Real Documentation exists. Online and in print. The reading of several of these is required to make the step from small time DNS admin to a big time one.
I have written The Concise Guide to DNS and BIND (by Nicolai Langfeldt, me), published by Que (ISBN 0-7897-2273-9). The book is much like this HOWTO, just more details, and a lot more of everything. It has also been translated to Polish and published as DNS i BIND by Helion ( http://helion.pl/ksiazki/dnsbin.htm, ISBN 83-7197-446-9). Now in 4th edition is DNS and BIND by Cricket Liu and P. Albitz from O'Reilly & Associates (ISBN 0-937175-82-X, affectionately known as the Cricket book). Another book is Linux DNS Server Administration, by Craig Hunt, published by Sybex (ISBN 0782127363), I have not read it yet. Another must for good DNS administration (or good anything for that matter) is Zen and the Art of Motorcycle Maintenance by Robert M. Pirsig.
Online you will find my book, along with tons of other books, available electronically as a subscription service at http://safari.informit.com/. There is stuff on http://www.dns.net/dnsrd/ (DNS Resources Directory), http://www.isc.org/bind.html; A FAQ, a reference manual (the ARM should be enclosed in the BIND distribution as well) as well as papers and protocol definitions and DNS hacks (these, and most, if not all, of the RFCs mentioned below, are also contained in the BIND distribution). I have not read most of these. The newsgroup news:comp.protocols.tcp-ip.domains is about DNS. In addition there are a number of RFCs about DNS, the most important are probably the ones listed here. Those that have BCP (Best Current Practice) numbers are highly recommended.
P. Vixie, Extension Mechanisms for DNS (EDNS0) August 1999.
BCP 20, H. Eidnes et. al. Classless IN-ADDR.ARPA delegation, March 1998. This is about CIDR, or classless subnet reverse lookups.
M. Andrews, Negative Caching of DNS Queries, March 1998. About negative caching and the $TTL zone file directive.
BCP 17, M. Hamilton and R. Wright, Use of DNS Aliases for Network Services, October 1997. About CNAME usage.
BCP 16, R. Elz et. al., Selection and Operation of Secondary DNS Servers, July 1997.
A. Gulbrandsen, P. Vixie, A DNS RR for specifying the location of services (DNS SRV), October 1996
Y. Rekhter, R. Moskowitz, D. Karrenberg, G. de Groot, E. Lear, Address Allocation for Private Internets, 02/29/1996.
D. Barr, Common DNS Operational and Configuration Errors, 02/28/1996.
B. Barr Errors in RFC 1912. Only available at http://www.cis.ohio-state.edu/~barr/rfc1912-errors.html
A. Romao, Tools for DNS debugging, 11/03/1994.
C. Farrell, M. Schulze, S. Pleitner, D. Baldoni, DNS Encoding of Geographical Location, 11/01/1994.
R. Ullmann, P. Mockapetris, L. Mamakos, C. Everhart, New DNS RR Definitions, 10/08/1990.
P. Mockapetris, Domain names - implementation and specification, 11/01/1987.
P. Mockapetris, Domain names - concepts and facilities, 11/01/1987.
M. Lottor, Domain administrators operations guide, 11/01/1987.
M. Stahl, Domain administrators guide, 11/01/1987.
C. Partridge, Mail routing and the domain system, 01/01/1986.