First, find out which registrars can register your domain name. For the generic top-level domains, this is easy: there's a list of registrars accredited by ICANN, the Internet Corporation for Assigned Names and Numbers, at http://www.icann.org...dited-list.html. For other domains, start at http://www.norid.no/domreg.html: each entry is a link to the registry for that particular top-level domain. While the registry may not process registration requests, most registries provide links to their registrars on their web sites.
choose a registrar. The registrars for a single top-level domain may
offer different prices for registration and various associated
services, such as hosting your zone on their name servers. For the
org), the cost of registration is usually
between $15 and $35 annually (the wholesale price -- which you
can't get, even if you "know
someone in the business" -- is $6 per year). For
other TLDs, the cost varies considerably.
Finally, register your domain name with the registrar. This is almost invariably a web-based process that involves specifying the domain name you want to register: personal information, such as your name, address, phone number and email address, and the domain names of the name servers you'll use (and possibly their IP addresses). Oh, and some means of allowing the registrar to bill you.
Choose your registrar wisely, and not solely on the basis of price. Some registrars offer notoriously poor customer service, and transferring to a different registrar is much more difficult than simply making the right decision the first time. Ask for recommendations from friends and colleagues, check newsgroups for sad tales of woe and, hypothetically, laudatory postings. And make sure you can work with the registrar the way you want to: using a web-based interface, if that's what you prefer, or via fax or a toll-free number (that they answer promptly).
Learn more about this topic from DNS & Bind Cookbook.
The DNS & BIND Cookbook presents solutions to the many problems faced by network administrators responsible for a name server. This title is an indispensable companion to DNS & BIND, 4th Edition, the definitive guide to the critical task of name server administration. The cookbook contains dozens of code recipes showing solutions to everyday problems, ranging from simple questions, like, "How do I get BIND?" to more advanced topics like providing name service for IPv6 addresses.