When you sign up with an ISP you are usually given some web server space to use. The URL for these web sites is generally something like www.ispname.net/~yourname. Although this may be good enough for personal home pages, a real business should invest in a domain name of their own.
The biggest problem with choosing a domain name is finding one that hasn't already been registered. Some names that have been registered are not currently in use and others have been abandoned. There are people who buy up domain names in hopes of selling that name to someone in the future. To check on the availability of a name here are several possibilities. My favorite place to buy domain names is GoDaddy.com the world's largest registrar.
A good domain name should give the user some idea about the name or nature of your business. Short names are easier to remember, advertise and enter into a browser. There used to be a limit to the length of your name to 23 characters. That limit is now 67 characters, so if a short name doesn't suit you or the name you really want is already taken, perhaps a longer name will do.
There is some debate about the use of hypens in domain names. I like them because it makes the name easier to read. Adding keywords (terms people may use in a search engine) to your domain name is a good idea. Adding hyphens helps search engines identify these keywords. The downside is that the domain name becomes hard to say (ie, about hyphen the hyphen web dot com).
There are seven common extensions you can get for your name. They are .org (usually reserved for non-profit organizations), .edu (for educational organizations), .gov (for government web sites), .net (for Internet service providers), .info (for informative website), .biz (for business websites) and .com (for commercial ventures).
There are new extensions cropping up all the time. New choices are .tv (usually for entertainment sites), .ws (stands for website), .name (for personal websites), .jobs (employment sites), and .mobi (websites designed for mobile devices). There are also many country specific extensions (.CA, .UK, .MX, .FR, .DK, .DE, .CH, .BE, .AT, .AU, .CZ).
If you're in business, my recommendation is to choose a .com extension, because they are still the easiest to remember. However if your .com name has been taken, or one of the new extensions appeals to you for some other reason, they work just as well.
Domain For Sale, Website For Sale, Portals For Sale
SlashRoot.Com offers domain name, fully developed web sites, and complete portals for sale. Also provides the entire range of domain name registration services.
Domain Name Discussion Forum and Premium Domains Directory
GotGreat.Com focuses on issues related to marketing of Generic DOT COM domain names. Provides its members many easy-to-use ePublishing resources to submit articles, news, and to participate in ongoing domain discussions. Free membership includes access to listing in GotGreatCom premium domains showcase.