Most often, free domains are available when you use free hosting. Usually, you would get a third-level domain, which is a subdomain of the hoster's site. Such domains are at a disadvantage, since users (if not totally novice) usually know that the domain belongs to a free low budget hosting. There is a possibility of obtaining a second level domain for free without any tricks. Many hosters register domains for the first year of their usage, when you purchase hosting for some time in advance.

For example, when you buy a hosting for a whole year, any hoster would allow you to get a domain in the.com, .net, .org, and other zones for free. There is also the possibility to register third level domains in national zones for free, however this requires their linking to some hosting (NS servers need to be specified).