There are many backordering companies who will grap the name as soon as it expires - If more than one person has backordered the name you will have to bid for it.
Backordering usually costs around $60 to start but names have gone up to about $300,000 in the bidding process in the past.
There are thousands of people who use these companies - do a whois on the domain - if it is currently reg'd with Network Solutions then place your backorder at www.snapnames.com because they will get the name for sure - you do not get billed unless they manage to get the name for you.
Oh - Many domains that are dropping are still grabbed because they quite often had traffic and incoming links to them.
I do know of a couple of companies that buy just about anything and everything that is dropping - they then "test" the name to see if it has traffic - if it does not they might release within a few weeks back into the general public - so you MAY get it then ???? --- If it has traffic they will keep it.
It depends on how much you want the name ??? It's a chance you have to take.
I don't understand why someone would pay to backorder a domain (which could be expensive) when the person dropping the domain would probably sell dirt cheap. Is there a reason for this that I'm not aware of?