It's very difficult to rely on our ability to catch a domain name as it has dropped and registered it before someone else does. Furthermore, most of the registrars don't even allow the better domains to be dropped, instead, placing them in online auctions. This is where back ordering comes into play. With back ordering services, you are able to pre-purchase a domain name that is about to expire, as long as the current owner fails to renew it themselves.
However, there is no guarantee you will be given the domain name, even if it expires due to other back ordering services offering the same opportunity to other people who are looking to snag a great domain name that's about to drop. Still, it definitely increases your chances of being able to scoop up some of the better domain names with existing traffic and page rank. POPULAR PLACE FOR BACK ORDERING SERVICES Here are a few of the more popular back ordering services:
www.NameJet.com ; www.SnapNames.com ; www.Pool.com