This may seem a novice question, but I've never bought a 'taken' domain name before, only new... This domain is about to expire, so how do I go about buying it?

The domain has no website present, so I guess I could use the whois info to simply get in touch and ask outright! Seems simple... but I see some sites offer a bidding style auction for sites that are due to expire (assuming this is not going to be reregistered). These sites take a commision of the sale, so where is the incentive to get this at a good price for me?

Has anyone used these domain name biddding sites?

Thanks D