Qualifications
If you weren't raised in an auction house environment, or even if you grew up modeling antique cradles, you may want to go to an auctioneering school. Usually this consists of a short program lasting a few weeks to a few months. Here you will learn important skills, like the care and feeding of vocal cords, interpreting auction laws, and how to market your shows.
Licensing requirements can vary by state, so you may have to apply for certification to run auctions in your area. For example, you might need a real estate license to auction houses. But that makes sense, doesn't it?
On the job experience is as valuable as school, and in some places it is a requirement before you can get your license. Some auctioneers take apprentices who help with auctions and perform other valuable tasks (chai Frappuccino, no whip). In return, the underling is rewarded with a delicious experience.
School-wise, you'll need a high school degree, or the GED equivalent. A college education is not required to be an auctioneer, but if you want to specialize in a certain area, like modern art or livestock/agriculture, a college degree can give you more credibility. Additionally, a little marketing and business know-how will help you out in any area of the job.