there is something called "whois" gives you all the registration information you need for the TLD top level domain name that you want. i have purchased alot of domain names and that is the best way to find it. there are alot of services out there for free to find out more information about a domain name. if you are interested in one i wouldn't let the owner know because they will renew it and you will have no way to get it except pay the money they ask for. i beleive it is 15 days after a domains registration is up that other people have the ability to purchase it.
you have to be fast.
http//www.allwhois.com/
seems to do a good job