You want to register a new domain name.
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/registrars/accredited-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.
 Think of a registrar as a domain name retailer. Their wholesalers are registration authorities, or registries, the organizations that manage the registration data itself. A single registrar may handle registration in many different top-level domains.
Next, 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 gTLDs (com, net, and 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).
1.6.4 See Also
Recipes Section 1.7 and Section 1.9, for registering name servers and changing registrars; and "Registering Your Zones" in Chapter 3 of DNS and BIND.
BIND Name Server Configuration
BIND Name Server Operations
Delegation and Registration
Interoperability and Upgrading
Resolvers and Programming
Logging and Troubleshooting