This is part of an introductory guide to buying and owning domain names, written by Mary Gardiner for LinuxChix in 2004. It is no longer being updated but is available for modification and republication under the Creative Commons Attribution-ShareAlike licence.
The last section of a domain name: the ".com", ".net", ".org", ".au" and so on is known as a "top level domain" (TLD). Although it's possible to have a arbitrarily large number of these, and there are some alternative domain name systems that advertise a large number of them (see OpenNIC for example), most of the Internet relies on the top level domains controlled by the Internet Corporation For Assigned Names and Numbers.
Basically, unless you're a sovereign nation, you're not going to get your own top level domain. At best, you may someday meet someone who controls one and is willing to give you a username@com email address — yes, that would be a valid address if .com had a mail server, which it doesn't seem to. You're going to purchase a second level or third level domain (fourth only in fairly rare cases).
The most common choice of vanity domain is one ending in .com, .net or .org. This isn't the original purpose of those top level domains, it was meant to go something like this:
There are some other international TLDs, see the generic TLD list.
If you're not US or multinational, you were meant to get a domain in your national top level domain (.au for Australia, .ca for Canada, see the full list).
Some people still protest that this should be respected. I don't run a multinational non-profit called "The Puzzling Organisation" so I should I really be able to register "puzzling.org"? However, the horse bolted from this particular starting gate some years ago now. Many .com addresses aren't owned by commercial enterprises etc etc.
My personal inclination is to explain this as due to an (understandable) lack of foresight by the original designers of the current system of TLDs. They don't seem to have considered that individuals would one day want a domain name. Nor was there space for products (like movies or soft drinks) to have their own domain name. I considered this issue seriously back in 2000, but while there were lots of people lecturing me on the correct use of the international TLDs, there didn't seem to be any place I could register a vanity domain and keep these people happy.
In the end, I found out Australia did have a second level domain for individuals (.id.au) but at the time you couldn't register third-level domains under .id.au (since July 2002 you can), you had to get a fourth level domain from the maintainers of such domains as wattle.id.au, dropbear.id.au or echidna.id.au. Much as I love our native flora and fauna, I thought it was too cutesy, and so "puzzling.org" it was.
Another thing about the top level domains is that the most popular international ones are pretty cluttered. As I said in the previous lesson, finding an English word under .com, .net or .org is difficult and has been for years.
Recently some small nations with their own TLDs have started selling second level domains internationally: .tv (Tuvalu) is probably the most popular of these. You may have better luck under these: they're available through many large registrars.
Unless you're intending to stick with the original purpose of the TLDs (I shan't criticise you: pots, kettles, all that), here are my suggestions:
First, decide whether you'd prefer to get something under your own country's TLD. Some countries still restrict them fairly tightly though and don't have any space for registration of vanity domains, so you may be out of luck. Others (like Australia) may require you to register a domain name that resembles your real name somehow.
If you can't get or don't want a localised TLD, choose the name first and the TLD second. Register the name in whatever TLD still has it free and which you like best. Geeks seem to have a slight preference for .net, I'd go for .com if you can get it, because everyone can spell it.
You could also look at the .name system
If you are based in a single nation outside the US, I'd suggest getting a domain under your country's TLD. Certainly, this is the most common thing to do in Australia. If you're based in the US you could consider the .us TLD, but I think it's much more common to use the international TLDs.
Otherwise you're probably after a .com and you should curse all the vanity domain holders and product domains that have made them difficult to find.
There are a few other relevant TLDs: .biz, .pro ...
An alternative is finding someone with a domain you like and asking them for a subdomain. I'd hesitate to do this: if they let their example.com registration lapse, you'll lose subdomain.example.com too. But it will normally be free, and I've heard it's a good way to get a domain with someone else's trademark in it (the registrars will take away your domain if someone complains loudly about trademark violation, even if your domain is clearly a comment on their trademark — pepsisucks.com or the like — but the registrars don't control subdomains). Of course, this doesn't guarantee you're safe from legal action.
You can use the "whois" tool on Linux to find out about a domain name. If the domain is taken, it will reply with the name and contact details of the registrant. If you get something like this, the domain isn't taken:
This used to only work for the international TLDs but seems a bit more reliable now. Still, it's better to ask a registrar.
Alternatively, you can go to the home page of one of the registrars, say register.com, type in the domain name and it will search all the TLDs in which it can sell domains (I see register.com does about 40) and tell you which TLDs your choice is available in. (Note that register.com is not the cheapest of registrars.)
You can't do this for subdomains of domains controlled by individuals, you'll need to contact the owner of the domain and ask them about availability.
Buying and owning a domain name: About the domain name system by Mary Gardiner is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.