Just google it...but don't try to get expired domains because it can be too harmful from search engines and those domains can deindex quickly. You can get expired domains in Networks, Link farms, etc. because those domains are good PR and domain age but Google never consider those type of domains.
Google is smart enough to detect when a new owner takes over a domain. They'd see the name server and hosting change, as well as the site content. So unless the domain has an especially spammy link profile, the domain should be fine to use. You likely won't get the full benefits of links they've built up in the past though. The domain could still have long term problems such as with blog or forum spam filters. Normally I'd try to find a brand new domain to use, but I have successfully built up sites with domain names that were previously used by others.