WhoIs Search for Domain Records
When you're looking to register a domain name, there's no better tool than a WhoIs search engine. Whois is way to look up names in a remote database, helpful for finding whether a domain name is available and, if not, to whom the domain is registered. If you query a particular name, and the search result finds no match, the domain name is probably available, and you can apply to register it at any domain registration service.
In addition to the sites we've listed at the above links, most domain name registration services have a WhoIs search engine at their site so you can check the availability of your desired domain name before you sign up with the company.
If you are interested in a domain name that is already registered to someone else but they don't seem to be using it, the best thing to do is look for the Administrative Contact in the WhoIs record and contact that person to see whether they are willing to part with the domain. If they are willing, please see the Domain Selling and Trading section on this site.
If you are interested in a domain name that is not available, but has expired, the best thing to do is get in touch with the Registrar through whom that domain was registered for the status of that domain. For help determining the registrar of the domain, please visit the Domain Transfers section of this site.