To find a good auction house, start at the National Auctioneers Association. This is a trade group for professional auction houses. You'll want to look for an auctioneer who has received a Certified Auctioneers Institute designation. This requires that members have at least two years of professional auction experience and take continuing education classes.
You'll want to interview the auction house. First ask how many auctions have been done in the area in the past month. Ask for references and make sure to follow up. You'll want to do as much research as you can.
If you are considering buying or selling at auction, a professional auctioneer can offer valuable advice. Auctionservices.com has created an Auction Community that is free and open to the public. Members include professional auctioneers who can answer your questions.