Make sure that what you are selling will cover the cost of moving it to the auction house.
I hate to disagree with Mom but most of the time the auctions are held right there at the property. And usually some of it is garage sale and some of it they auction and they handle everything.

I think what matters is how much stuff and how much value we are talking. If it is a a slew of stuff auction it... otherwise just have a garage sale and set the prices low and take all offers.