How does one auction?

I don't know if this would be right for me, or what the interest level would be, but Vividcon announced signups for this year's Auction and it's got me wondering about how vidders set the various parameters available: "fandoms [you'll] work in, how the song will be chosen (as long as both parties are happy with the final choice), preferred styles of music, how much input the bidder can have on clip choices, etc." Do any of you have insights?

Just idle speculation at this point, but am curious, in case I do decide to give it a try, this year or some other year. I've never done anything more than Festivids for vid-to-order.

ETA: Uhhhh okay I signed up! We will see how this goes!