There are backordering services that will always tell you, tell you sometimes, and never tell you. NameJet will only tell you if at least 3 people have backordered it.
The best way to do this is to determine what the domain name is worth to you and then only spend that. If it's worth $8 to you, then don't backorder it. Hand-register it if possible. If it's worth $15-20 to you, then backorder it at one of the less expensive sites like GoDaddy or Dynadot. And so on and so forth at companies like DropCatch, NameJet, and Snapnames, the more expensive options.
You'll find that unless the domain name is really good, no one else is backordering it.