This can be a tricky one, because you may find that popular domains have been registered - But how did they become popular ? Only by becoming marketed in the correct way
So you start with a domain registra and sample with a few names and see of they are available.
A couple of weeks ago, I came across http://www.expireddomains.net which enables you to search for domains which are coming up to expiry or have recently expired. This also give you some history of the domain, ie how may backlinks are registered in Google / MSN etc.
*** Although beware using this kind of site to find a domain, because you may find a domain that has been blacklisted by most of the Search Engines as it may have been used for unscrupulous reasons ***
If a domain has been sandboxed by Google, then you have got a 1% chance of getting this out of Sandbox and back into organic search
