Basically, the site spells out how it works in its extensive "Customer Care" section. I'd be happy to help you with specific SkyAuction questions. I have successfully bid on several auctions, and I have been quite pleased with the customer service and the things I won.
In a nutshell, make sure to read all of the info provided on the actual description page for each auction. For instance, many of the hotel stays ('Bid per night and choose your length of stay . . .') require an addl. per night fee (usually $32) tacked on to your winning bid. It is spelled out in the listing though. Also. each winning bid warrants a $15 service fee tacked on to your total.
One other thing: if you refer someone to SA and they register with the site, you earn a $5 credit toward a future winning bid. Recently I was able to subtract $25 from my winning bid payment because five freinds had registered. That was nice.