In one of my posts on my blog, I explain the domain expiration process in detail and outline the exact steps you can take in order to snatch/backorder the domain of your choice. http://www.domainmarvelous.com/featured_articles/expiring-domain-names-2/ Snapnames.com, pool.com and enom.com are some of the popular sites to backorder domains. Godaddy's backorder system is not that successful, IMO. Recently, name.com launched its own domain back ordering system, named Domain Nabber. You may want to check this one out too.
I think you need to use pool, snapnames and namejet. All 3 of them, they you should get it every time, or at least in an auction.
It must depend the domain name under which "Registrar" Example: If Registrar = Register.com, better backorder at snapnames.com