http://www.domainsherpa.com/chris-ambler-domain-name-expiration/ they talk about the best drop catching services. I'm guessing you already know that the owner can still renew the name over a month after expiration. Some people will wait till after month then transfer it rather than pay redemption. Anyways good luck with that
In that case it would go to GoDaddy auction 1 week before the owner loses the right to renew it (which then is a really small chance). The highest bid gets the domain in case owner fails to renew.