There are premium tools to help you find expired domains such as
SpamZilla,
DomCop and
RegisterCompass. There is also a free tool,
Expired Domains, that work fairly well in finding a decent expired domain if you put some time and effort into it. There are some limitations however, such as being able to mostly only find partial match domains (PMDs) and exact match domains (EMDs), while missing out on branded domains, because you are only limited to searching for keywords in the domain names themselves.